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	$124.95	10.266%	$137.7774	$137.78	$137.80	$137.80
Purchase #2	$213.44	7.406%	$229.2474	$229.25	$229.25	$229.20
Purchase #3	$222.72	9.398%	$243.6512	$243.65	$243.65	$243.70
Purchase #4	$80.41	13.714%	$91.4374	$91.44	$91.45	$91.40
Purchase #5	$236.31	6.279%	$251.1479	$251.15	$251.15	$251.10
Purchase #6	$100.94	11.780%	$112.8307	$112.83	$112.85	$112.80
Purchase #7	$120.99	7.526%	$130.0957	$130.10	$130.10	$130.10
7 purchase totals =	$1,099.76		$1,196.1877	$1,196.20	$1,196.25	$1,196.10