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	$155.70	4.602%	$162.8653	$162.87	$162.85	$162.90
Purchase #2	$222.30	12.816%	$250.79	$250.79	$250.80	$250.80
Purchase #3	$147.44	5.432%	$155.4489	$155.45	$155.45	$155.40
Purchase #4	$29.69	9.375%	$32.4734	$32.47	$32.45	$32.50
Purchase #5	$139.95	4.864%	$146.7572	$146.76	$146.75	$146.80
Purchase #6	$176.83	12.701%	$199.2892	$199.29	$199.30	$199.30
Purchase #7	$150.87	8.315%	$163.4148	$163.41	$163.40	$163.40
7 purchase totals =	$1,022.78		$1,111.0388	$1,111.04	$1,111.00	$1,111.10