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	$175.87	5.262%	$185.1243	$185.12	$185.10	$185.10
Purchase #2	$123.88	13.855%	$141.0436	$141.04	$141.05	$141.00
Purchase #3	$225.94	4.840%	$236.8755	$236.88	$236.90	$236.90
Purchase #4	$33.40	5.687%	$35.2995	$35.30	$35.30	$35.30
Purchase #5	$223.31	5.489%	$235.5675	$235.57	$235.55	$235.60
Purchase #6	$6.67	6.139%	$7.0795	$7.08	$7.10	$7.10
Purchase #7	$77.59	10.259%	$85.55	$85.55	$85.55	$85.60
7 purchase totals =	$866.66		$926.5399	$926.54	$926.55	$926.60