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	$17.68	3.870%	$18.3642	$18.36	$18.35	$18.40
Purchase #2	$53.51	3.804%	$55.5455	$55.55	$55.55	$55.50
Purchase #3	$129.71	7.290%	$139.1659	$139.17	$139.15	$139.20
Purchase #4	$159.42	3.130%	$164.4098	$164.41	$164.40	$164.40
Purchase #5	$230.80	12.281%	$259.1445	$259.14	$259.15	$259.10
Purchase #6	$215.80	13.723%	$245.4142	$245.41	$245.40	$245.40
Purchase #7	$173.53	4.804%	$181.8664	$181.87	$181.85	$181.90
7 purchase totals =	$980.45		$1,063.9105	$1,063.91	$1,063.85	$1,063.90