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	$247.61	10.788%	$274.3222	$274.32	$274.30	$274.30
Purchase #2	$13.75	13.744%	$15.6398	$15.64	$15.65	$15.60
Purchase #3	$80.63	10.628%	$89.1994	$89.20	$89.20	$89.20
Purchase #4	$117.97	4.310%	$123.0545	$123.05	$123.05	$123.10
Purchase #5	$100.56	8.444%	$109.0513	$109.05	$109.05	$109.10
Purchase #6	$64.87	13.218%	$73.4445	$73.44	$73.45	$73.40
Purchase #7	$36.99	6.814%	$39.5105	$39.51	$39.50	$39.50
7 purchase totals =	$662.38		$724.2222	$724.21	$724.20	$724.20