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	$191.39	4.466%	$199.9375	$199.94	$199.95	$199.90
Purchase #2	$225.98	5.250%	$237.844	$237.84	$237.85	$237.80
Purchase #3	$195.81	13.713%	$222.6614	$222.66	$222.65	$222.70
Purchase #4	$200.55	11.252%	$223.1159	$223.12	$223.10	$223.10
Purchase #5	$54.46	5.248%	$57.3181	$57.32	$57.30	$57.30
Purchase #6	$24.30	5.392%	$25.6103	$25.61	$25.60	$25.60
Purchase #7	$31.74	3.728%	$32.9233	$32.92	$32.90	$32.90
7 purchase totals =	$924.23		$999.4105	$999.41	$999.35	$999.30