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	$127.81	13.329%	$144.8458	$144.85	$144.85	$144.80
Purchase #2	$174.25	11.586%	$194.4386	$194.44	$194.45	$194.40
Purchase #3	$30.62	10.748%	$33.911	$33.91	$33.90	$33.90
Purchase #4	$50.73	4.186%	$52.8536	$52.85	$52.85	$52.90
Purchase #5	$128.88	13.645%	$146.4657	$146.47	$146.45	$146.50
Purchase #6	$223.27	13.599%	$253.6325	$253.63	$253.65	$253.60
Purchase #7	$229.71	12.767%	$259.0371	$259.04	$259.05	$259.00
7 purchase totals =	$965.27		$1,085.1843	$1,085.19	$1,085.20	$1,085.10