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	$165.30	4.740%	$173.1352	$173.14	$173.15	$173.10
Purchase #2	$51.77	13.352%	$58.6823	$58.68	$58.70	$58.70
Purchase #3	$139.81	4.118%	$145.5674	$145.57	$145.55	$145.60
Purchase #4	$249.75	4.301%	$260.4917	$260.49	$260.50	$260.50
Purchase #5	$162.54	5.371%	$171.27	$171.27	$171.25	$171.30
Purchase #6	$139.51	10.783%	$154.5534	$154.55	$154.55	$154.60
Purchase #7	$36.96	4.760%	$38.7193	$38.72	$38.70	$38.70
7 purchase totals =	$945.64		$1,002.4193	$1,002.42	$1,002.40	$1,002.50