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	$226.91	7.467%	$243.8534	$243.85	$243.85	$243.90
Purchase #2	$174.98	9.487%	$191.5804	$191.58	$191.60	$191.60
Purchase #3	$172.82	9.677%	$189.5438	$189.54	$189.55	$189.50
Purchase #4	$24.31	6.624%	$25.9203	$25.92	$25.90	$25.90
Purchase #5	$66.81	5.740%	$70.6449	$70.64	$70.65	$70.60
Purchase #6	$56.66	4.641%	$59.2896	$59.29	$59.30	$59.30
Purchase #7	$185.98	6.671%	$198.3867	$198.39	$198.40	$198.40
7 purchase totals =	$908.47		$979.2191	$979.21	$979.25	$979.20