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	$203.41	12.521%	$228.879	$228.88	$228.90	$228.90
Purchase #2	$90.29	11.467%	$100.6436	$100.64	$100.65	$100.60
Purchase #3	$46.69	9.342%	$51.0518	$51.05	$51.05	$51.10
Purchase #4	$239.77	8.716%	$260.6684	$260.67	$260.65	$260.70
Purchase #5	$92.74	7.322%	$99.5304	$99.53	$99.55	$99.50
Purchase #6	$183.32	6.595%	$195.41	$195.41	$195.40	$195.40
Purchase #7	$73.79	11.612%	$82.3585	$82.36	$82.35	$82.40
7 purchase totals =	$930.01		$1,018.5417	$1,018.54	$1,018.55	$1,018.60