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	$149.31	8.510%	$162.0163	$162.02	$162.00	$162.00
Purchase #2	$175.48	10.492%	$193.8914	$193.89	$193.90	$193.90
Purchase #3	$239.52	13.356%	$271.5103	$271.51	$271.50	$271.50
Purchase #4	$78.65	13.640%	$89.3779	$89.38	$89.40	$89.40
Purchase #5	$142.59	8.194%	$154.2738	$154.27	$154.25	$154.30
Purchase #6	$79.46	4.333%	$82.903	$82.90	$82.90	$82.90
Purchase #7	$207.52	12.174%	$232.7835	$232.78	$232.80	$232.80
7 purchase totals =	$1,072.53		$1,186.7562	$1,186.75	$1,186.75	$1,186.80