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	$102.37	10.291%	$112.9049	$112.90	$112.90	$112.90
Purchase #2	$57.76	6.249%	$61.3694	$61.37	$61.35	$61.40
Purchase #3	$53.56	7.197%	$57.4147	$57.41	$57.40	$57.40
Purchase #4	$90.50	5.592%	$95.5608	$95.56	$95.55	$95.60
Purchase #5	$12.58	7.718%	$13.5509	$13.55	$13.55	$13.60
Purchase #6	$154.36	11.340%	$171.8644	$171.86	$171.85	$171.90
Purchase #7	$144.67	10.814%	$160.3146	$160.31	$160.30	$160.30
7 purchase totals =	$615.80		$672.9797	$672.96	$672.90	$673.10