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	$223.57	5.454%	$235.7635	$235.76	$235.75	$235.80
Purchase #2	$38.71	5.590%	$40.8739	$40.87	$40.85	$40.90
Purchase #3	$148.56	11.493%	$165.634	$165.63	$165.65	$165.60
Purchase #4	$165.56	13.620%	$188.1093	$188.11	$188.10	$188.10
Purchase #5	$12.90	13.134%	$14.5943	$14.59	$14.60	$14.60
Purchase #6	$151.53	13.647%	$172.2093	$172.21	$172.20	$172.20
Purchase #7	$242.45	12.664%	$273.1539	$273.15	$273.15	$273.20
7 purchase totals =	$983.28		$1,090.3382	$1,090.32	$1,090.30	$1,090.40