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	$216.74	3.130%	$223.524	$223.52	$223.50	$223.50
Purchase #2	$53.61	4.512%	$56.0289	$56.03	$56.05	$56.00
Purchase #3	$154.76	13.424%	$175.535	$175.54	$175.55	$175.50
Purchase #4	$35.30	13.630%	$40.1114	$40.11	$40.10	$40.10
Purchase #5	$77.35	3.640%	$80.1655	$80.17	$80.15	$80.20
Purchase #6	$101.56	11.419%	$113.1571	$113.16	$113.15	$113.20
Purchase #7	$50.46	12.126%	$56.5788	$56.58	$56.60	$56.60
7 purchase totals =	$689.78		$745.1007	$745.11	$745.10	$745.10