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	$181.59	3.398%	$187.7604	$187.76	$187.75	$187.80
Purchase #2	$89.39	8.270%	$96.7826	$96.78	$96.80	$96.80
Purchase #3	$17.66	6.648%	$18.834	$18.83	$18.85	$18.80
Purchase #4	$244.39	4.194%	$254.6397	$254.64	$254.65	$254.60
Purchase #5	$25.34	3.760%	$26.2928	$26.29	$26.30	$26.30
Purchase #6	$179.54	6.747%	$191.6536	$191.65	$191.65	$191.70
Purchase #7	$147.79	7.267%	$158.5299	$158.53	$158.55	$158.50
7 purchase totals =	$885.70		$934.4930	$934.48	$934.55	$934.50