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	$232.86	13.662%	$264.6733	$264.67	$264.65	$264.70
Purchase #2	$65.98	9.116%	$71.9947	$71.99	$72.00	$72.00
Purchase #3	$191.33	9.695%	$209.8794	$209.88	$209.90	$209.90
Purchase #4	$132.41	6.577%	$141.1186	$141.12	$141.10	$141.10
Purchase #5	$99.31	5.557%	$104.8287	$104.83	$104.85	$104.80
Purchase #6	$161.50	11.657%	$180.3261	$180.33	$180.35	$180.30
Purchase #7	$57.75	10.388%	$63.7491	$63.75	$63.75	$63.70
7 purchase totals =	$941.14		$1,036.5699	$1,036.57	$1,036.60	$1,036.50