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	$85.83	5.140%	$90.2417	$90.24	$90.25	$90.20
Purchase #2	$7.88	5.301%	$8.2977	$8.30	$8.30	$8.30
Purchase #3	$238.43	11.267%	$265.2939	$265.29	$265.30	$265.30
Purchase #4	$100.54	3.171%	$103.7281	$103.73	$103.75	$103.70
Purchase #5	$75.48	4.173%	$78.6298	$78.63	$78.65	$78.60
Purchase #6	$72.26	6.417%	$76.8969	$76.90	$76.90	$76.90
Purchase #7	$76.86	13.236%	$87.0332	$87.03	$87.05	$87.00
7 purchase totals =	$657.28		$710.1213	$710.12	$710.20	$710.00