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	$77.35	10.389%	$85.3859	$85.39	$85.40	$85.40
Purchase #2	$125.72	11.462%	$140.13	$140.13	$140.15	$140.10
Purchase #3	$183.42	3.418%	$189.6893	$189.69	$189.70	$189.70
Purchase #4	$110.52	7.845%	$119.1903	$119.19	$119.20	$119.20
Purchase #5	$77.29	6.421%	$82.2528	$82.25	$82.25	$82.30
Purchase #6	$181.80	10.308%	$200.5399	$200.54	$200.55	$200.50
Purchase #7	$118.95	10.234%	$131.1233	$131.12	$131.10	$131.10
7 purchase totals =	$875.05		$948.3115	$948.31	$948.35	$948.30