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	$148.90	4.586%	$155.7286	$155.73	$155.75	$155.70
Purchase #2	$198.46	11.759%	$221.7969	$221.80	$221.80	$221.80
Purchase #3	$97.33	8.761%	$105.8571	$105.86	$105.85	$105.90
Purchase #4	$155.70	13.449%	$176.6401	$176.64	$176.65	$176.60
Purchase #5	$199.90	6.495%	$212.8835	$212.88	$212.90	$212.90
Purchase #6	$94.42	7.466%	$101.4694	$101.47	$101.45	$101.50
Purchase #7	$229.83	5.225%	$241.8386	$241.84	$241.85	$241.80
7 purchase totals =	$1,124.54		$1,216.2142	$1,216.22	$1,216.25	$1,216.20