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	$210.56	11.753%	$235.3071	$235.31	$235.30	$235.30
Purchase #2	$105.63	12.739%	$119.0862	$119.09	$119.10	$119.10
Purchase #3	$98.29	8.408%	$106.5542	$106.55	$106.55	$106.60
Purchase #4	$87.80	3.846%	$91.1768	$91.18	$91.20	$91.20
Purchase #5	$203.96	11.211%	$226.826	$226.83	$226.85	$226.80
Purchase #6	$85.72	6.447%	$91.2464	$91.25	$91.25	$91.20
Purchase #7	$131.47	11.400%	$146.4576	$146.46	$146.45	$146.50
7 purchase totals =	$923.43		$1,016.6543	$1,016.67	$1,016.70	$1,016.70