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	$246.79	3.468%	$255.3487	$255.35	$255.35	$255.30
Purchase #2	$94.45	5.310%	$99.4653	$99.47	$99.45	$99.50
Purchase #3	$174.46	11.362%	$194.2821	$194.28	$194.30	$194.30
Purchase #4	$136.48	7.469%	$146.6737	$146.67	$146.65	$146.70
Purchase #5	$51.57	4.651%	$53.9685	$53.97	$53.95	$54.00
Purchase #6	$144.71	5.206%	$152.2436	$152.24	$152.25	$152.20
Purchase #7	$242.30	4.430%	$253.0339	$253.03	$253.05	$253.00
7 purchase totals =	$1,090.76		$1,155.0158	$1,155.01	$1,155.00	$1,155.00