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	$92.62	9.574%	$101.4874	$101.49	$101.50	$101.50
Purchase #2	$219.71	8.216%	$237.7614	$237.76	$237.75	$237.80
Purchase #3	$139.78	8.245%	$151.3049	$151.30	$151.30	$151.30
Purchase #4	$81.91	10.294%	$90.3418	$90.34	$90.35	$90.30
Purchase #5	$65.45	11.194%	$72.7765	$72.78	$72.80	$72.80
Purchase #6	$58.94	13.761%	$67.0507	$67.05	$67.05	$67.10
Purchase #7	$26.46	9.580%	$28.9949	$28.99	$29.00	$29.00
7 purchase totals =	$684.87		$749.7176	$749.71	$749.75	$749.80