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	$227.82	5.515%	$240.3843	$240.38	$240.40	$240.40
Purchase #2	$120.64	7.336%	$129.4902	$129.49	$129.50	$129.50
Purchase #3	$66.95	6.208%	$71.1063	$71.11	$71.10	$71.10
Purchase #4	$143.92	6.244%	$152.9064	$152.91	$152.90	$152.90
Purchase #5	$213.74	4.182%	$222.6786	$222.68	$222.70	$222.70
Purchase #6	$60.83	11.454%	$67.7975	$67.80	$67.80	$67.80
Purchase #7	$118.35	12.757%	$133.4479	$133.45	$133.45	$133.40
7 purchase totals =	$952.25		$1,017.8112	$1,017.82	$1,017.85	$1,017.80