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	$162.38	5.450%	$171.2297	$171.23	$171.25	$171.20
Purchase #2	$235.75	8.415%	$255.5884	$255.59	$255.60	$255.60
Purchase #3	$48.39	13.362%	$54.8559	$54.86	$54.85	$54.90
Purchase #4	$81.80	13.160%	$92.5649	$92.56	$92.55	$92.60
Purchase #5	$175.49	7.469%	$188.5973	$188.60	$188.60	$188.60
Purchase #6	$44.73	11.419%	$49.8377	$49.84	$49.85	$49.80
Purchase #7	$73.54	12.414%	$82.6693	$82.67	$82.65	$82.70
7 purchase totals =	$822.08		$895.3432	$895.35	$895.35	$895.40