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	$62.50	3.601%	$64.7506	$64.75	$64.75	$64.80
Purchase #2	$123.73	6.453%	$131.7143	$131.71	$131.70	$131.70
Purchase #3	$159.48	7.682%	$171.7313	$171.73	$171.75	$171.70
Purchase #4	$63.34	12.802%	$71.4488	$71.45	$71.45	$71.40
Purchase #5	$99.27	12.692%	$111.8693	$111.87	$111.85	$111.90
Purchase #6	$134.27	4.359%	$140.1228	$140.12	$140.10	$140.10
Purchase #7	$101.98	11.695%	$113.9066	$113.91	$113.90	$113.90
7 purchase totals =	$744.57		$805.5437	$805.54	$805.50	$805.50