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	$104.25	7.740%	$112.319	$112.32	$112.30	$112.30
Purchase #2	$80.82	11.761%	$90.3252	$90.33	$90.35	$90.30
Purchase #3	$65.86	13.588%	$74.8091	$74.81	$74.80	$74.80
Purchase #4	$80.77	10.489%	$89.242	$89.24	$89.25	$89.20
Purchase #5	$34.73	7.515%	$37.34	$37.34	$37.35	$37.30
Purchase #6	$203.70	10.144%	$224.3633	$224.36	$224.35	$224.40
Purchase #7	$232.95	6.473%	$248.0289	$248.03	$248.05	$248.00
7 purchase totals =	$803.08		$876.4275	$876.43	$876.45	$876.30