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	$183.93	3.608%	$190.5662	$190.57	$190.55	$190.60
Purchase #2	$19.37	7.799%	$20.8807	$20.88	$20.90	$20.90
Purchase #3	$192.63	3.663%	$199.686	$199.69	$199.70	$199.70
Purchase #4	$18.67	11.123%	$20.7467	$20.75	$20.75	$20.70
Purchase #5	$78.68	13.119%	$89.002	$89.00	$89.00	$89.00
Purchase #6	$209.83	12.815%	$236.7197	$236.72	$236.70	$236.70
Purchase #7	$176.26	8.135%	$190.5988	$190.60	$190.60	$190.60
7 purchase totals =	$879.37		$948.2001	$948.21	$948.20	$948.20