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	$198.80	11.318%	$221.3002	$221.30	$221.30	$221.30
Purchase #2	$167.95	9.648%	$184.1538	$184.15	$184.15	$184.20
Purchase #3	$242.69	9.127%	$264.8403	$264.84	$264.85	$264.80
Purchase #4	$73.75	6.791%	$78.7584	$78.76	$78.75	$78.80
Purchase #5	$159.50	5.806%	$168.7606	$168.76	$168.75	$168.80
Purchase #6	$48.38	12.642%	$54.4962	$54.50	$54.50	$54.50
Purchase #7	$210.85	10.668%	$233.3435	$233.34	$233.35	$233.30
7 purchase totals =	$1,101.92		$1,205.6530	$1,205.65	$1,205.65	$1,205.70