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	$175.39	3.213%	$181.0253	$181.03	$181.05	$181.00
Purchase #2	$129.39	10.530%	$143.0148	$143.01	$143.00	$143.00
Purchase #3	$83.46	4.116%	$86.8952	$86.90	$86.90	$86.90
Purchase #4	$99.92	11.813%	$111.7235	$111.72	$111.70	$111.70
Purchase #5	$13.49	9.166%	$14.7265	$14.73	$14.75	$14.70
Purchase #6	$172.88	10.779%	$191.5147	$191.51	$191.50	$191.50
Purchase #7	$124.93	10.323%	$137.8265	$137.83	$137.85	$137.80
7 purchase totals =	$799.46		$866.7265	$866.73	$866.75	$866.60