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	$157.41	3.371%	$162.7163	$162.72	$162.70	$162.70
Purchase #2	$84.62	4.785%	$88.6691	$88.67	$88.65	$88.70
Purchase #3	$92.27	7.752%	$99.4228	$99.42	$99.40	$99.40
Purchase #4	$59.59	6.477%	$63.4496	$63.45	$63.45	$63.40
Purchase #5	$84.89	10.103%	$93.4664	$93.47	$93.45	$93.50
Purchase #6	$196.75	6.499%	$209.5368	$209.54	$209.55	$209.50
Purchase #7	$158.69	13.640%	$180.3353	$180.34	$180.35	$180.30
7 purchase totals =	$834.22		$897.5963	$897.61	$897.55	$897.50