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	$85.56	7.316%	$91.8196	$91.82	$91.80	$91.80
Purchase #2	$246.38	3.560%	$255.1511	$255.15	$255.15	$255.20
Purchase #3	$238.89	12.326%	$268.3356	$268.34	$268.35	$268.30
Purchase #4	$173.96	9.321%	$190.1748	$190.17	$190.15	$190.20
Purchase #5	$146.42	10.816%	$162.2568	$162.26	$162.25	$162.30
Purchase #6	$96.72	3.720%	$100.318	$100.32	$100.30	$100.30
Purchase #7	$25.83	8.527%	$28.0325	$28.03	$28.05	$28.00
7 purchase totals =	$1,013.76		$1,096.0884	$1,096.09	$1,096.05	$1,096.10