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	$116.54	3.188%	$120.2553	$120.26	$120.25	$120.30
Purchase #2	$9.82	3.236%	$10.1378	$10.14	$10.15	$10.10
Purchase #3	$145.95	13.374%	$165.4694	$165.47	$165.45	$165.50
Purchase #4	$169.56	6.486%	$180.5577	$180.56	$180.55	$180.60
Purchase #5	$73.69	12.312%	$82.7627	$82.76	$82.75	$82.80
Purchase #6	$34.66	6.870%	$37.0411	$37.04	$37.05	$37.00
Purchase #7	$145.81	11.108%	$162.0066	$162.01	$162.00	$162.00
7 purchase totals =	$696.03		$758.2306	$758.24	$758.20	$758.30