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	$191.40	4.172%	$199.3852	$199.39	$199.40	$199.40
Purchase #2	$64.98	4.391%	$67.8333	$67.83	$67.85	$67.80
Purchase #3	$221.65	5.290%	$233.3753	$233.38	$233.40	$233.40
Purchase #4	$86.61	6.601%	$92.3271	$92.33	$92.35	$92.30
Purchase #5	$161.58	4.563%	$168.9529	$168.95	$168.95	$169.00
Purchase #6	$37.40	12.613%	$42.1173	$42.12	$42.10	$42.10
Purchase #7	$168.70	11.419%	$187.9639	$187.96	$187.95	$188.00
7 purchase totals =	$932.32		$991.9550	$991.96	$992.00	$992.00