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	$158.74	5.184%	$166.9691	$166.97	$166.95	$167.00
Purchase #2	$76.30	9.793%	$83.7721	$83.77	$83.75	$83.80
Purchase #3	$123.96	3.182%	$127.9044	$127.90	$127.90	$127.90
Purchase #4	$90.82	9.123%	$99.1055	$99.11	$99.10	$99.10
Purchase #5	$129.88	4.670%	$135.9454	$135.95	$135.95	$135.90
Purchase #6	$165.66	5.283%	$174.4118	$174.41	$174.40	$174.40
Purchase #7	$149.59	11.273%	$166.4533	$166.45	$166.45	$166.50
7 purchase totals =	$894.95		$954.5616	$954.56	$954.50	$954.60