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	$142.33	5.364%	$149.9646	$149.96	$149.95	$150.00
Purchase #2	$167.61	12.201%	$188.0601	$188.06	$188.05	$188.10
Purchase #3	$149.86	10.507%	$165.6058	$165.61	$165.60	$165.60
Purchase #4	$106.60	10.627%	$117.9284	$117.93	$117.95	$117.90
Purchase #5	$35.64	5.570%	$37.6251	$37.63	$37.65	$37.60
Purchase #6	$90.88	7.352%	$97.5615	$97.56	$97.55	$97.60
Purchase #7	$114.60	11.332%	$127.5865	$127.59	$127.60	$127.60
7 purchase totals =	$807.52		$884.3320	$884.34	$884.35	$884.40