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	$79.95	4.191%	$83.3007	$83.30	$83.30	$83.30
Purchase #2	$210.47	3.737%	$218.3353	$218.34	$218.35	$218.30
Purchase #3	$240.99	9.687%	$264.3347	$264.33	$264.35	$264.30
Purchase #4	$153.84	7.309%	$165.0842	$165.08	$165.10	$165.10
Purchase #5	$38.87	6.669%	$41.4622	$41.46	$41.45	$41.50
Purchase #6	$100.51	11.863%	$112.4335	$112.43	$112.45	$112.40
Purchase #7	$243.89	8.851%	$265.4767	$265.48	$265.50	$265.50
7 purchase totals =	$1,068.52		$1,150.4273	$1,150.42	$1,150.50	$1,150.40