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	$192.87	4.686%	$201.9079	$201.91	$201.90	$201.90
Purchase #2	$247.25	3.278%	$255.3549	$255.35	$255.35	$255.40
Purchase #3	$139.59	4.240%	$145.5086	$145.51	$145.50	$145.50
Purchase #4	$229.28	3.680%	$237.7175	$237.72	$237.70	$237.70
Purchase #5	$213.41	4.195%	$222.3625	$222.36	$222.35	$222.40
Purchase #6	$19.88	5.712%	$21.0155	$21.02	$21.00	$21.00
Purchase #7	$95.32	10.746%	$105.5631	$105.56	$105.55	$105.60
7 purchase totals =	$1,137.60		$1,189.4300	$1,189.43	$1,189.35	$1,189.50