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	$215.47	6.789%	$230.0983	$230.10	$230.10	$230.10
Purchase #2	$212.78	10.854%	$235.8751	$235.88	$235.90	$235.90
Purchase #3	$52.40	6.779%	$55.9522	$55.95	$55.95	$56.00
Purchase #4	$212.51	11.841%	$237.6733	$237.67	$237.65	$237.70
Purchase #5	$96.27	9.178%	$105.1057	$105.11	$105.10	$105.10
Purchase #6	$11.39	4.347%	$11.8851	$11.89	$11.90	$11.90
Purchase #7	$211.48	5.764%	$223.6697	$223.67	$223.65	$223.70
7 purchase totals =	$1,012.30		$1,100.2594	$1,100.27	$1,100.25	$1,100.40