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	$157.96	8.121%	$170.7879	$170.79	$170.80	$170.80
Purchase #2	$26.56	8.267%	$28.7557	$28.76	$28.75	$28.80
Purchase #3	$52.90	13.261%	$59.9151	$59.92	$59.90	$59.90
Purchase #4	$234.31	3.325%	$242.1008	$242.10	$242.10	$242.10
Purchase #5	$30.44	3.795%	$31.5952	$31.60	$31.60	$31.60
Purchase #6	$195.43	9.270%	$213.5464	$213.55	$213.55	$213.50
Purchase #7	$196.45	13.477%	$222.9256	$222.93	$222.95	$222.90
7 purchase totals =	$894.05		$969.6267	$969.65	$969.65	$969.60