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	$142.93	5.293%	$150.4953	$150.50	$150.50	$150.50
Purchase #2	$140.78	6.140%	$149.4239	$149.42	$149.40	$149.40
Purchase #3	$203.85	7.213%	$218.5537	$218.55	$218.55	$218.60
Purchase #4	$152.86	12.405%	$171.8223	$171.82	$171.80	$171.80
Purchase #5	$116.48	13.173%	$131.8239	$131.82	$131.80	$131.80
Purchase #6	$62.58	13.844%	$71.2436	$71.24	$71.25	$71.20
Purchase #7	$204.71	7.335%	$219.7255	$219.73	$219.75	$219.70
7 purchase totals =	$1,024.19		$1,113.0882	$1,113.08	$1,113.05	$1,113.00