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	$43.59	5.441%	$45.9617	$45.96	$45.95	$46.00
Purchase #2	$135.92	11.293%	$151.2694	$151.27	$151.25	$151.30
Purchase #3	$131.81	10.437%	$145.567	$145.57	$145.55	$145.60
Purchase #4	$195.59	10.139%	$215.4209	$215.42	$215.40	$215.40
Purchase #5	$125.37	11.450%	$139.7249	$139.72	$139.70	$139.70
Purchase #6	$143.58	5.169%	$151.0017	$151.00	$151.00	$151.00
Purchase #7	$86.45	3.150%	$89.1732	$89.17	$89.15	$89.20
7 purchase totals =	$862.31		$938.1188	$938.11	$938.00	$938.20