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	$59.33	10.813%	$65.7454	$65.75	$65.75	$65.70
Purchase #2	$183.76	3.528%	$190.2431	$190.24	$190.25	$190.20
Purchase #3	$41.63	8.746%	$45.271	$45.27	$45.25	$45.30
Purchase #4	$250.25	10.814%	$277.312	$277.31	$277.30	$277.30
Purchase #5	$59.35	3.340%	$61.3323	$61.33	$61.35	$61.30
Purchase #6	$50.53	6.461%	$53.7947	$53.79	$53.80	$53.80
Purchase #7	$207.78	6.303%	$220.8764	$220.88	$220.90	$220.90
7 purchase totals =	$852.63		$914.5749	$914.57	$914.60	$914.50