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	$109.73	6.538%	$116.9041	$116.90	$116.90	$116.90
Purchase #2	$199.45	12.741%	$224.8619	$224.86	$224.85	$224.90
Purchase #3	$20.79	12.152%	$23.3164	$23.32	$23.30	$23.30
Purchase #4	$145.47	3.589%	$150.6909	$150.69	$150.70	$150.70
Purchase #5	$37.54	10.582%	$41.5125	$41.51	$41.50	$41.50
Purchase #6	$222.26	10.524%	$245.6506	$245.65	$245.65	$245.70
Purchase #7	$238.56	5.361%	$251.3492	$251.35	$251.35	$251.30
7 purchase totals =	$973.80		$1,054.2856	$1,054.28	$1,054.25	$1,054.30