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	$51.88	6.113%	$55.0514	$55.05	$55.05	$55.10
Purchase #2	$178.81	10.668%	$197.8855	$197.89	$197.90	$197.90
Purchase #3	$45.30	6.496%	$48.2427	$48.24	$48.25	$48.20
Purchase #4	$173.30	6.376%	$184.3496	$184.35	$184.35	$184.30
Purchase #5	$165.61	4.215%	$172.5905	$172.59	$172.60	$172.60
Purchase #6	$135.25	4.194%	$140.9224	$140.92	$140.90	$140.90
Purchase #7	$248.41	5.173%	$261.2602	$261.26	$261.25	$261.30
7 purchase totals =	$998.56		$1,060.3023	$1,060.30	$1,060.30	$1,060.30