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	$129.67	5.515%	$136.8213	$136.82	$136.80	$136.80
Purchase #2	$68.81	3.265%	$71.0566	$71.06	$71.05	$71.10
Purchase #3	$128.60	7.102%	$137.7332	$137.73	$137.75	$137.70
Purchase #4	$236.53	13.867%	$269.3296	$269.33	$269.35	$269.30
Purchase #5	$73.76	11.491%	$82.2358	$82.24	$82.25	$82.20
Purchase #6	$88.47	11.477%	$98.6237	$98.62	$98.60	$98.60
Purchase #7	$168.32	13.291%	$190.6914	$190.69	$190.70	$190.70
7 purchase totals =	$894.16		$986.4916	$986.49	$986.50	$986.40