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	$132.52	10.249%	$146.102	$146.10	$146.10	$146.10
Purchase #2	$58.87	5.816%	$62.2939	$62.29	$62.30	$62.30
Purchase #3	$174.40	8.658%	$189.4996	$189.50	$189.50	$189.50
Purchase #4	$202.77	6.681%	$216.3171	$216.32	$216.30	$216.30
Purchase #5	$88.56	3.178%	$91.3744	$91.37	$91.35	$91.40
Purchase #6	$86.55	3.490%	$89.5706	$89.57	$89.55	$89.60
Purchase #7	$216.74	4.639%	$226.7946	$226.79	$226.80	$226.80
7 purchase totals =	$960.41		$1,021.9522	$1,021.94	$1,021.90	$1,022.00