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	$153.90	10.237%	$169.6547	$169.65	$169.65	$169.70
Purchase #2	$75.37	9.524%	$82.5482	$82.55	$82.55	$82.50
Purchase #3	$200.88	13.693%	$228.3865	$228.39	$228.40	$228.40
Purchase #4	$233.43	5.497%	$246.2616	$246.26	$246.25	$246.30
Purchase #5	$79.40	12.224%	$89.1059	$89.11	$89.10	$89.10
Purchase #6	$92.74	11.224%	$103.1491	$103.15	$103.15	$103.10
Purchase #7	$224.60	12.334%	$252.3022	$252.30	$252.30	$252.30
7 purchase totals =	$1,060.32		$1,171.4082	$1,171.41	$1,171.40	$1,171.40