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	$249.71	3.794%	$259.184	$259.18	$259.20	$259.20
Purchase #2	$70.88	3.630%	$73.4529	$73.45	$73.45	$73.50
Purchase #3	$91.38	3.485%	$94.5646	$94.56	$94.55	$94.60
Purchase #4	$195.72	4.360%	$204.2534	$204.25	$204.25	$204.30
Purchase #5	$101.66	13.560%	$115.4451	$115.45	$115.45	$115.40
Purchase #6	$82.78	8.357%	$89.6979	$89.70	$89.70	$89.70
Purchase #7	$225.39	10.634%	$249.358	$249.36	$249.35	$249.40
7 purchase totals =	$1,017.52		$1,085.9559	$1,085.95	$1,085.95	$1,086.10