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	$205.81	7.809%	$221.8817	$221.88	$221.90	$221.90
Purchase #2	$99.74	12.644%	$112.3511	$112.35	$112.35	$112.40
Purchase #3	$21.61	4.247%	$22.5278	$22.53	$22.55	$22.50
Purchase #4	$247.42	3.365%	$255.7457	$255.75	$255.75	$255.70
Purchase #5	$209.36	5.192%	$220.23	$220.23	$220.25	$220.20
Purchase #6	$204.85	6.838%	$218.8576	$218.86	$218.85	$218.90
Purchase #7	$88.91	11.717%	$99.3276	$99.33	$99.35	$99.30
7 purchase totals =	$1,077.70		$1,150.9215	$1,150.93	$1,151.00	$1,150.90