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	$34.34	8.475%	$37.2503	$37.25	$37.25	$37.30
Purchase #2	$163.26	9.118%	$178.146	$178.15	$178.15	$178.10
Purchase #3	$196.91	5.568%	$207.8739	$207.87	$207.85	$207.90
Purchase #4	$55.91	6.278%	$59.42	$59.42	$59.40	$59.40
Purchase #5	$89.35	7.495%	$96.0468	$96.05	$96.05	$96.00
Purchase #6	$35.29	9.130%	$38.512	$38.51	$38.50	$38.50
Purchase #7	$247.33	10.566%	$273.4629	$273.46	$273.45	$273.50
7 purchase totals =	$822.39		$890.7119	$890.71	$890.65	$890.70