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	$169.35	3.458%	$175.2061	$175.21	$175.20	$175.20
Purchase #2	$194.76	6.613%	$207.6395	$207.64	$207.65	$207.60
Purchase #3	$47.69	10.318%	$52.6107	$52.61	$52.60	$52.60
Purchase #4	$85.56	4.561%	$89.4624	$89.46	$89.45	$89.50
Purchase #5	$32.69	8.110%	$35.3412	$35.34	$35.35	$35.30
Purchase #6	$80.56	4.748%	$84.385	$84.39	$84.40	$84.40
Purchase #7	$61.89	7.453%	$66.5027	$66.50	$66.50	$66.50
7 purchase totals =	$672.50		$711.1476	$711.15	$711.15	$711.10