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	$33.29	11.630%	$37.1616	$37.16	$37.15	$37.20
Purchase #2	$139.95	11.735%	$156.3731	$156.37	$156.35	$156.40
Purchase #3	$166.67	9.371%	$182.2886	$182.29	$182.30	$182.30
Purchase #4	$151.58	13.483%	$172.0175	$172.02	$172.00	$172.00
Purchase #5	$89.49	12.370%	$100.5599	$100.56	$100.55	$100.60
Purchase #6	$170.89	11.745%	$190.961	$190.96	$190.95	$191.00
Purchase #7	$216.56	3.735%	$224.6485	$224.65	$224.65	$224.60
7 purchase totals =	$968.43		$1,064.0102	$1,064.01	$1,063.95	$1,064.10