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	$46.87	11.494%	$52.2572	$52.26	$52.25	$52.30
Purchase #2	$169.88	6.800%	$181.4318	$181.43	$181.45	$181.40
Purchase #3	$174.25	12.609%	$196.2212	$196.22	$196.20	$196.20
Purchase #4	$106.40	6.843%	$113.681	$113.68	$113.70	$113.70
Purchase #5	$141.54	7.687%	$152.4202	$152.42	$152.40	$152.40
Purchase #6	$71.92	5.567%	$75.9238	$75.92	$75.90	$75.90
Purchase #7	$217.69	13.827%	$247.79	$247.79	$247.80	$247.80
7 purchase totals =	$928.55		$1,019.7252	$1,019.72	$1,019.70	$1,019.70