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	$83.51	13.748%	$94.991	$94.99	$95.00	$95.00
Purchase #2	$41.90	9.178%	$45.7456	$45.75	$45.75	$45.70
Purchase #3	$29.96	13.344%	$33.9579	$33.96	$33.95	$34.00
Purchase #4	$223.73	4.758%	$234.3751	$234.38	$234.40	$234.40
Purchase #5	$50.75	12.200%	$56.9415	$56.94	$56.95	$56.90
Purchase #6	$103.69	11.699%	$115.8207	$115.82	$115.80	$115.80
Purchase #7	$74.99	5.194%	$78.885	$78.89	$78.90	$78.90
7 purchase totals =	$608.53		$660.7168	$660.73	$660.75	$660.70