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	$59.74	3.166%	$61.6314	$61.63	$61.65	$61.60
Purchase #2	$147.53	6.111%	$156.5456	$156.55	$156.55	$156.50
Purchase #3	$241.38	5.158%	$253.8304	$253.83	$253.85	$253.80
Purchase #4	$73.42	12.682%	$82.7311	$82.73	$82.75	$82.70
Purchase #5	$173.57	4.626%	$181.5993	$181.60	$181.60	$181.60
Purchase #6	$191.89	13.542%	$217.8757	$217.88	$217.90	$217.90
Purchase #7	$176.52	13.466%	$200.2902	$200.29	$200.30	$200.30
7 purchase totals =	$1,064.05		$1,154.5037	$1,154.51	$1,154.60	$1,154.40