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	$244.34	4.531%	$255.411	$255.41	$255.40	$255.40
Purchase #2	$164.50	4.229%	$171.4567	$171.46	$171.45	$171.50
Purchase #3	$241.73	12.408%	$271.7239	$271.72	$271.70	$271.70
Purchase #4	$124.92	12.266%	$140.2427	$140.24	$140.25	$140.20
Purchase #5	$130.82	6.626%	$139.4881	$139.49	$139.50	$139.50
Purchase #6	$179.37	5.572%	$189.3645	$189.36	$189.35	$189.40
Purchase #7	$207.83	13.673%	$236.2466	$236.25	$236.25	$236.20
7 purchase totals =	$1,293.51		$1,403.9335	$1,403.93	$1,403.90	$1,403.90