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	$215.85	3.645%	$223.7177	$223.72	$223.70	$223.70
Purchase #2	$48.67	10.807%	$53.9298	$53.93	$53.95	$53.90
Purchase #3	$188.92	3.339%	$195.228	$195.23	$195.25	$195.20
Purchase #4	$65.30	9.601%	$71.5695	$71.57	$71.55	$71.60
Purchase #5	$82.44	8.236%	$89.2298	$89.23	$89.25	$89.20
Purchase #6	$87.59	13.306%	$99.2447	$99.24	$99.25	$99.20
Purchase #7	$127.29	13.109%	$143.9764	$143.98	$144.00	$144.00
7 purchase totals =	$816.06		$876.8959	$876.90	$876.95	$876.80