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	$64.85	10.496%	$71.6567	$71.66	$71.65	$71.70
Purchase #2	$74.54	7.247%	$79.9419	$79.94	$79.95	$79.90
Purchase #3	$102.31	7.160%	$109.6354	$109.64	$109.65	$109.60
Purchase #4	$155.48	4.266%	$162.1128	$162.11	$162.10	$162.10
Purchase #5	$160.43	4.350%	$167.4087	$167.41	$167.40	$167.40
Purchase #6	$44.33	8.178%	$47.9553	$47.96	$47.95	$48.00
Purchase #7	$65.49	10.362%	$72.2761	$72.28	$72.30	$72.30
7 purchase totals =	$667.43		$710.9869	$711.00	$711.00	$711.00