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	$30.28	11.677%	$33.8158	$33.82	$33.80	$33.80
Purchase #2	$98.52	7.562%	$105.9701	$105.97	$105.95	$106.00
Purchase #3	$133.52	12.795%	$150.6039	$150.60	$150.60	$150.60
Purchase #4	$138.35	7.632%	$148.9089	$148.91	$148.90	$148.90
Purchase #5	$187.32	4.227%	$195.238	$195.24	$195.25	$195.20
Purchase #6	$129.46	10.323%	$142.8242	$142.82	$142.80	$142.80
Purchase #7	$71.39	9.774%	$78.3677	$78.37	$78.35	$78.40
7 purchase totals =	$788.84		$855.7286	$855.73	$855.65	$855.70