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	$148.61	4.231%	$154.8977	$154.90	$154.90	$154.90
Purchase #2	$225.67	8.781%	$245.4861	$245.49	$245.50	$245.50
Purchase #3	$63.86	13.324%	$72.3687	$72.37	$72.35	$72.40
Purchase #4	$155.36	9.792%	$170.5729	$170.57	$170.55	$170.60
Purchase #5	$17.52	13.221%	$19.8363	$19.84	$19.85	$19.80
Purchase #6	$68.89	13.567%	$78.2363	$78.24	$78.25	$78.20
Purchase #7	$227.79	9.364%	$249.1203	$249.12	$249.10	$249.10
7 purchase totals =	$907.70		$990.5183	$990.53	$990.50	$990.50