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	$184.57	3.664%	$191.3326	$191.33	$191.35	$191.30
Purchase #2	$147.48	3.454%	$152.574	$152.57	$152.55	$152.60
Purchase #3	$232.37	13.839%	$264.5277	$264.53	$264.55	$264.50
Purchase #4	$144.35	7.149%	$154.6696	$154.67	$154.65	$154.70
Purchase #5	$36.77	11.280%	$40.9177	$40.92	$40.90	$40.90
Purchase #6	$149.39	12.464%	$168.01	$168.01	$168.00	$168.00
Purchase #7	$105.48	5.658%	$111.4481	$111.45	$111.45	$111.40
7 purchase totals =	$1,000.41		$1,083.4797	$1,083.48	$1,083.45	$1,083.40