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	$147.27	13.314%	$166.8775	$166.88	$166.90	$166.90
Purchase #2	$103.89	3.206%	$107.2207	$107.22	$107.20	$107.20
Purchase #3	$101.60	3.482%	$105.1377	$105.14	$105.15	$105.10
Purchase #4	$35.77	3.757%	$37.1139	$37.11	$37.10	$37.10
Purchase #5	$211.27	6.164%	$224.2927	$224.29	$224.30	$224.30
Purchase #6	$148.62	11.164%	$165.2119	$165.21	$165.20	$165.20
Purchase #7	$195.27	8.249%	$211.3778	$211.38	$211.40	$211.40
7 purchase totals =	$943.69		$1,017.2322	$1,017.23	$1,017.25	$1,017.20