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	$160.53	4.565%	$167.8582	$167.86	$167.85	$167.90
Purchase #2	$66.36	9.837%	$72.8878	$72.89	$72.90	$72.90
Purchase #3	$40.90	6.168%	$43.4227	$43.42	$43.40	$43.40
Purchase #4	$209.30	11.327%	$233.0074	$233.01	$233.00	$233.00
Purchase #5	$110.53	7.768%	$119.116	$119.12	$119.10	$119.10
Purchase #6	$200.98	10.113%	$221.3051	$221.31	$221.30	$221.30
Purchase #7	$246.43	9.185%	$269.0646	$269.06	$269.05	$269.10
7 purchase totals =	$1,035.03		$1,126.6618	$1,126.67	$1,126.60	$1,126.70