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	$121.72	4.626%	$127.3508	$127.35	$127.35	$127.40
Purchase #2	$17.63	5.472%	$18.5947	$18.59	$18.60	$18.60
Purchase #3	$89.67	10.614%	$99.1876	$99.19	$99.20	$99.20
Purchase #4	$203.41	7.199%	$218.0535	$218.05	$218.05	$218.10
Purchase #5	$223.95	13.636%	$254.4878	$254.49	$254.50	$254.50
Purchase #6	$162.77	10.627%	$180.0676	$180.07	$180.05	$180.10
Purchase #7	$79.27	9.189%	$86.5541	$86.55	$86.55	$86.60
7 purchase totals =	$898.42		$984.2961	$984.29	$984.30	$984.50