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	$108.73	9.225%	$118.7603	$118.76	$118.75	$118.80
Purchase #2	$231.61	10.711%	$256.4177	$256.42	$256.40	$256.40
Purchase #3	$161.42	10.594%	$178.5208	$178.52	$178.50	$178.50
Purchase #4	$178.41	6.432%	$189.8853	$189.89	$189.90	$189.90
Purchase #5	$157.59	9.627%	$172.7612	$172.76	$172.75	$172.80
Purchase #6	$33.41	4.273%	$34.8376	$34.84	$34.85	$34.80
Purchase #7	$97.34	5.721%	$102.9088	$102.91	$102.90	$102.90
7 purchase totals =	$968.51		$1,054.0917	$1,054.10	$1,054.05	$1,054.10