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	$207.80	5.302%	$218.8176	$218.82	$218.80	$218.80
Purchase #2	$73.67	5.346%	$77.6084	$77.61	$77.60	$77.60
Purchase #3	$246.46	9.864%	$270.7708	$270.77	$270.75	$270.80
Purchase #4	$128.28	9.370%	$140.2998	$140.30	$140.30	$140.30
Purchase #5	$75.41	9.315%	$82.4344	$82.43	$82.45	$82.40
Purchase #6	$172.79	13.827%	$196.6817	$196.68	$196.70	$196.70
Purchase #7	$89.81	6.606%	$95.7428	$95.74	$95.75	$95.70
7 purchase totals =	$994.22		$1,082.3555	$1,082.35	$1,082.35	$1,082.30