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	$123.60	7.499%	$132.8688	$132.87	$132.85	$132.90
Purchase #2	$158.35	6.623%	$168.8375	$168.84	$168.85	$168.80
Purchase #3	$65.63	8.587%	$71.2656	$71.27	$71.25	$71.30
Purchase #4	$249.78	13.303%	$283.0082	$283.01	$283.00	$283.00
Purchase #5	$7.90	10.471%	$8.7272	$8.73	$8.75	$8.70
Purchase #6	$206.40	6.375%	$219.558	$219.56	$219.55	$219.60
Purchase #7	$209.93	8.148%	$227.0351	$227.04	$227.05	$227.00
7 purchase totals =	$1,021.59		$1,111.3004	$1,111.32	$1,111.30	$1,111.30