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	$39.81	3.855%	$41.3447	$41.34	$41.35	$41.30
Purchase #2	$20.71	3.821%	$21.5013	$21.50	$21.50	$21.50
Purchase #3	$161.27	6.505%	$171.7606	$171.76	$171.75	$171.80
Purchase #4	$168.67	12.187%	$189.2258	$189.23	$189.25	$189.20
Purchase #5	$144.54	7.838%	$155.869	$155.87	$155.85	$155.90
Purchase #6	$211.97	7.236%	$227.3081	$227.31	$227.30	$227.30
Purchase #7	$210.81	3.596%	$218.3907	$218.39	$218.40	$218.40
7 purchase totals =	$957.78		$1,025.4002	$1,025.40	$1,025.40	$1,025.40