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	$61.35	10.450%	$67.7611	$67.76	$67.75	$67.80
Purchase #2	$182.25	5.593%	$192.4432	$192.44	$192.45	$192.40
Purchase #3	$102.88	8.399%	$111.5209	$111.52	$111.50	$111.50
Purchase #4	$208.73	11.177%	$232.0598	$232.06	$232.05	$232.10
Purchase #5	$204.82	8.739%	$222.7192	$222.72	$222.70	$222.70
Purchase #6	$78.86	5.845%	$83.4694	$83.47	$83.45	$83.50
Purchase #7	$203.70	7.126%	$218.2157	$218.22	$218.20	$218.20
7 purchase totals =	$1,042.59		$1,128.1893	$1,128.19	$1,128.10	$1,128.20