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	$162.39	8.318%	$175.8976	$175.90	$175.90	$175.90
Purchase #2	$67.83	7.522%	$72.9322	$72.93	$72.95	$72.90
Purchase #3	$58.84	9.413%	$64.3786	$64.38	$64.40	$64.40
Purchase #4	$93.57	12.484%	$105.2513	$105.25	$105.25	$105.30
Purchase #5	$43.37	6.367%	$46.1314	$46.13	$46.15	$46.10
Purchase #6	$82.90	11.115%	$92.1143	$92.11	$92.10	$92.10
Purchase #7	$225.88	12.326%	$253.722	$253.72	$253.70	$253.70
7 purchase totals =	$734.78		$810.4274	$810.42	$810.45	$810.40