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	$154.64	10.726%	$171.2267	$171.23	$171.25	$171.20
Purchase #2	$34.46	4.588%	$36.041	$36.04	$36.05	$36.00
Purchase #3	$245.90	3.462%	$254.4131	$254.41	$254.40	$254.40
Purchase #4	$100.31	6.123%	$106.452	$106.45	$106.45	$106.50
Purchase #5	$153.48	11.682%	$171.4095	$171.41	$171.40	$171.40
Purchase #6	$59.68	11.508%	$66.548	$66.55	$66.55	$66.50
Purchase #7	$191.99	7.633%	$206.6446	$206.64	$206.65	$206.60
7 purchase totals =	$940.46		$1,012.7349	$1,012.73	$1,012.75	$1,012.60