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	$98.87	12.399%	$111.1289	$111.13	$111.15	$111.10
Purchase #2	$100.35	4.299%	$104.664	$104.66	$104.65	$104.70
Purchase #3	$96.92	5.146%	$101.9075	$101.91	$101.90	$101.90
Purchase #4	$219.34	10.635%	$242.6668	$242.67	$242.65	$242.70
Purchase #5	$75.39	4.616%	$78.87	$78.87	$78.85	$78.90
Purchase #6	$177.31	7.327%	$190.3015	$190.30	$190.30	$190.30
Purchase #7	$197.28	12.817%	$222.5654	$222.57	$222.55	$222.60
7 purchase totals =	$965.46		$1,052.1041	$1,052.11	$1,052.05	$1,052.20