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	$201.86	7.676%	$217.3548	$217.35	$217.35	$217.40
Purchase #2	$175.50	4.355%	$183.143	$183.14	$183.15	$183.10
Purchase #3	$166.54	3.408%	$172.2157	$172.22	$172.20	$172.20
Purchase #4	$80.97	10.245%	$89.2654	$89.27	$89.25	$89.30
Purchase #5	$45.76	12.165%	$51.3267	$51.33	$51.35	$51.30
Purchase #6	$69.38	12.819%	$78.2738	$78.27	$78.25	$78.30
Purchase #7	$191.54	9.791%	$210.2937	$210.29	$210.30	$210.30
7 purchase totals =	$931.55		$1,001.8731	$1,001.87	$1,001.85	$1,001.90