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	$89.43	13.311%	$101.334	$101.33	$101.35	$101.30
Purchase #2	$151.55	11.335%	$168.7282	$168.73	$168.75	$168.70
Purchase #3	$12.60	13.507%	$14.3019	$14.30	$14.30	$14.30
Purchase #4	$222.90	10.496%	$246.2956	$246.30	$246.30	$246.30
Purchase #5	$69.28	11.473%	$77.2285	$77.23	$77.25	$77.20
Purchase #6	$83.79	7.313%	$89.9176	$89.92	$89.90	$89.90
Purchase #7	$181.25	11.154%	$201.4666	$201.47	$201.45	$201.50
7 purchase totals =	$810.80		$899.2724	$899.28	$899.30	$899.20