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	$80.61	6.349%	$85.7279	$85.73	$85.75	$85.70
Purchase #2	$245.91	3.696%	$254.9988	$255.00	$255.00	$255.00
Purchase #3	$9.71	4.653%	$10.1618	$10.16	$10.15	$10.20
Purchase #4	$164.91	11.445%	$183.7839	$183.78	$183.80	$183.80
Purchase #5	$148.31	3.137%	$152.9625	$152.96	$152.95	$153.00
Purchase #6	$64.53	12.648%	$72.6918	$72.69	$72.70	$72.70
Purchase #7	$40.45	4.858%	$42.4151	$42.42	$42.40	$42.40
7 purchase totals =	$754.43		$802.7418	$802.74	$802.75	$802.80