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	$103.34	8.543%	$112.1683	$112.17	$112.15	$112.20
Purchase #2	$232.58	13.347%	$263.6225	$263.62	$263.60	$263.60
Purchase #3	$23.30	9.287%	$25.4639	$25.46	$25.45	$25.50
Purchase #4	$92.40	7.565%	$99.3901	$99.39	$99.40	$99.40
Purchase #5	$170.27	11.146%	$189.2483	$189.25	$189.25	$189.20
Purchase #6	$159.55	8.220%	$172.665	$172.67	$172.65	$172.70
Purchase #7	$16.89	9.866%	$18.5564	$18.56	$18.55	$18.60
7 purchase totals =	$798.33		$881.1145	$881.12	$881.05	$881.20