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	$165.86	8.756%	$180.3827	$180.38	$180.40	$180.40
Purchase #2	$76.31	8.776%	$83.007	$83.01	$83.00	$83.00
Purchase #3	$205.85	7.800%	$221.9063	$221.91	$221.90	$221.90
Purchase #4	$183.55	12.160%	$205.8697	$205.87	$205.85	$205.90
Purchase #5	$64.72	6.354%	$68.8323	$68.83	$68.85	$68.80
Purchase #6	$174.72	6.205%	$185.5614	$185.56	$185.55	$185.60
Purchase #7	$215.95	3.185%	$222.828	$222.83	$222.85	$222.80
7 purchase totals =	$1,086.96		$1,168.3874	$1,168.39	$1,168.40	$1,168.40