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	$169.93	10.596%	$187.9358	$187.94	$187.95	$187.90
Purchase #2	$120.66	8.195%	$130.5481	$130.55	$130.55	$130.50
Purchase #3	$50.86	7.620%	$54.7355	$54.74	$54.75	$54.70
Purchase #4	$175.85	4.671%	$184.064	$184.06	$184.05	$184.10
Purchase #5	$174.79	12.603%	$196.8188	$196.82	$196.80	$196.80
Purchase #6	$74.44	11.408%	$82.9321	$82.93	$82.95	$82.90
Purchase #7	$210.39	13.768%	$239.3565	$239.36	$239.35	$239.40
7 purchase totals =	$976.92		$1,076.3908	$1,076.40	$1,076.40	$1,076.30