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	$187.90	12.357%	$211.1188	$211.12	$211.10	$211.10
Purchase #2	$44.64	7.822%	$48.1317	$48.13	$48.15	$48.10
Purchase #3	$110.38	6.375%	$117.4167	$117.42	$117.40	$117.40
Purchase #4	$26.92	5.405%	$28.375	$28.38	$28.40	$28.40
Purchase #5	$35.76	13.650%	$40.6412	$40.64	$40.65	$40.60
Purchase #6	$57.65	7.296%	$61.8561	$61.86	$61.85	$61.90
Purchase #7	$185.49	10.470%	$204.9108	$204.91	$204.90	$204.90
7 purchase totals =	$648.74		$712.4503	$712.46	$712.45	$712.40