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	$47.85	12.338%	$53.7537	$53.75	$53.75	$53.80
Purchase #2	$118.89	10.420%	$131.2783	$131.28	$131.30	$131.30
Purchase #3	$211.66	9.546%	$231.8651	$231.87	$231.85	$231.90
Purchase #4	$48.54	4.865%	$50.9015	$50.90	$50.90	$50.90
Purchase #5	$104.91	5.639%	$110.8259	$110.83	$110.85	$110.80
Purchase #6	$30.83	7.778%	$33.228	$33.23	$33.25	$33.20
Purchase #7	$225.93	6.425%	$240.446	$240.45	$240.45	$240.40
7 purchase totals =	$788.61		$852.2985	$852.31	$852.35	$852.30