Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.73	3.258%	$225.8562	$225.86	$225.85	$225.90
Purchase #2	$116.99	10.673%	$129.4763	$129.48	$129.50	$129.50
Purchase #3	$208.58	7.742%	$224.7283	$224.73	$224.75	$224.70
Purchase #4	$94.42	11.490%	$105.2689	$105.27	$105.25	$105.30
Purchase #5	$149.46	4.392%	$156.0243	$156.02	$156.00	$156.00
Purchase #6	$174.76	13.546%	$198.433	$198.43	$198.45	$198.40
Purchase #7	$103.31	7.568%	$111.1285	$111.13	$111.15	$111.10
7 purchase totals =	$1,066.25		$1,150.9155	$1,150.92	$1,150.95	$1,150.90