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	$110.91	5.481%	$116.989	$116.99	$117.00	$117.00
Purchase #2	$222.50	3.165%	$229.5421	$229.54	$229.55	$229.50
Purchase #3	$86.35	3.424%	$89.3066	$89.31	$89.30	$89.30
Purchase #4	$149.89	8.593%	$162.77	$162.77	$162.75	$162.80
Purchase #5	$238.80	4.741%	$250.1215	$250.12	$250.10	$250.10
Purchase #6	$139.38	4.459%	$145.595	$145.60	$145.60	$145.60
Purchase #7	$99.90	10.405%	$110.2946	$110.29	$110.30	$110.30
7 purchase totals =	$1,047.73		$1,104.6188	$1,104.62	$1,104.60	$1,104.60