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	$220.97	12.384%	$248.3349	$248.33	$248.35	$248.30
Purchase #2	$97.43	8.415%	$105.6287	$105.63	$105.65	$105.60
Purchase #3	$152.86	4.432%	$159.6348	$159.63	$159.65	$159.60
Purchase #4	$53.74	5.864%	$56.8913	$56.89	$56.90	$56.90
Purchase #5	$55.37	12.851%	$62.4856	$62.49	$62.50	$62.50
Purchase #6	$225.78	6.578%	$240.6318	$240.63	$240.65	$240.60
Purchase #7	$126.34	3.554%	$130.8301	$130.83	$130.85	$130.80
7 purchase totals =	$932.49		$1,004.4372	$1,004.43	$1,004.55	$1,004.30