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	$104.52	13.714%	$118.8539	$118.85	$118.85	$118.90
Purchase #2	$29.66	13.788%	$33.7495	$33.75	$33.75	$33.70
Purchase #3	$229.61	8.437%	$248.9822	$248.98	$249.00	$249.00
Purchase #4	$61.38	3.796%	$63.71	$63.71	$63.70	$63.70
Purchase #5	$131.53	9.200%	$143.6308	$143.63	$143.65	$143.60
Purchase #6	$230.39	5.643%	$243.3909	$243.39	$243.40	$243.40
Purchase #7	$147.31	13.650%	$167.4178	$167.42	$167.40	$167.40
7 purchase totals =	$934.40		$1,019.7351	$1,019.73	$1,019.75	$1,019.70