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	$113.91	4.661%	$119.2193	$119.22	$119.20	$119.20
Purchase #2	$18.65	10.250%	$20.5616	$20.56	$20.55	$20.60
Purchase #3	$239.49	10.254%	$264.0473	$264.05	$264.05	$264.00
Purchase #4	$146.85	6.547%	$156.4643	$156.46	$156.45	$156.50
Purchase #5	$188.97	11.447%	$210.6014	$210.60	$210.60	$210.60
Purchase #6	$189.72	10.436%	$209.5192	$209.52	$209.50	$209.50
Purchase #7	$147.73	4.487%	$154.3586	$154.36	$154.35	$154.40
7 purchase totals =	$1,045.32		$1,134.7717	$1,134.77	$1,134.70	$1,134.80