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	$225.81	12.535%	$254.1153	$254.12	$254.10	$254.10
Purchase #2	$63.98	13.691%	$72.7395	$72.74	$72.75	$72.70
Purchase #3	$103.89	13.449%	$117.8622	$117.86	$117.85	$117.90
Purchase #4	$94.51	12.859%	$106.663	$106.66	$106.65	$106.70
Purchase #5	$238.80	10.678%	$264.2991	$264.30	$264.30	$264.30
Purchase #6	$180.91	10.181%	$199.3284	$199.33	$199.35	$199.30
Purchase #7	$59.83	4.103%	$62.2848	$62.28	$62.30	$62.30
7 purchase totals =	$967.73		$1,077.2923	$1,077.29	$1,077.30	$1,077.30