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	$183.67	11.451%	$204.7021	$204.70	$204.70	$204.70
Purchase #2	$212.48	4.612%	$222.2796	$222.28	$222.30	$222.30
Purchase #3	$153.63	12.317%	$172.5526	$172.55	$172.55	$172.60
Purchase #4	$155.32	12.435%	$174.634	$174.63	$174.65	$174.60
Purchase #5	$162.82	13.874%	$185.4096	$185.41	$185.40	$185.40
Purchase #6	$223.88	4.146%	$233.1621	$233.16	$233.15	$233.20
Purchase #7	$35.30	13.385%	$40.0249	$40.02	$40.00	$40.00
7 purchase totals =	$1,127.10		$1,232.7649	$1,232.75	$1,232.75	$1,232.80