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	$71.40	4.263%	$74.4438	$74.44	$74.45	$74.40
Purchase #2	$65.87	8.846%	$71.6969	$71.70	$71.70	$71.70
Purchase #3	$223.45	4.851%	$234.2896	$234.29	$234.30	$234.30
Purchase #4	$152.95	7.424%	$164.305	$164.31	$164.30	$164.30
Purchase #5	$248.81	13.152%	$281.5335	$281.53	$281.55	$281.50
Purchase #6	$115.73	11.361%	$128.8781	$128.88	$128.90	$128.90
Purchase #7	$27.51	13.128%	$31.1215	$31.12	$31.10	$31.10
7 purchase totals =	$905.72		$986.2684	$986.27	$986.30	$986.20