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	$180.45	10.316%	$199.0652	$199.07	$199.05	$199.10
Purchase #2	$208.82	12.330%	$234.5675	$234.57	$234.55	$234.60
Purchase #3	$123.92	12.755%	$139.726	$139.73	$139.75	$139.70
Purchase #4	$36.78	12.644%	$41.4305	$41.43	$41.45	$41.40
Purchase #5	$244.41	9.729%	$268.1886	$268.19	$268.20	$268.20
Purchase #6	$25.72	8.423%	$27.8864	$27.89	$27.90	$27.90
Purchase #7	$104.80	3.455%	$108.4208	$108.42	$108.40	$108.40
7 purchase totals =	$924.90		$1,019.2850	$1,019.30	$1,019.30	$1,019.30