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	$142.69	3.324%	$147.433	$147.43	$147.45	$147.40
Purchase #2	$142.47	8.615%	$154.7438	$154.74	$154.75	$154.70
Purchase #3	$82.96	3.488%	$85.8536	$85.85	$85.85	$85.90
Purchase #4	$105.82	13.679%	$120.2951	$120.30	$120.30	$120.30
Purchase #5	$159.56	3.220%	$164.6978	$164.70	$164.70	$164.70
Purchase #6	$104.67	11.251%	$116.4464	$116.45	$116.45	$116.40
Purchase #7	$218.82	4.214%	$228.0411	$228.04	$228.05	$228.00
7 purchase totals =	$956.99		$1,017.5108	$1,017.51	$1,017.55	$1,017.40