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	$94.88	10.184%	$104.5426	$104.54	$104.55	$104.50
Purchase #2	$60.46	3.209%	$62.4002	$62.40	$62.40	$62.40
Purchase #3	$85.56	10.790%	$94.7919	$94.79	$94.80	$94.80
Purchase #4	$200.84	12.391%	$225.7261	$225.73	$225.75	$225.70
Purchase #5	$99.47	11.820%	$111.2274	$111.23	$111.25	$111.20
Purchase #6	$160.32	12.829%	$180.8875	$180.89	$180.90	$180.90
Purchase #7	$63.66	8.554%	$69.1055	$69.11	$69.10	$69.10
7 purchase totals =	$765.19		$848.6812	$848.69	$848.75	$848.60