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	$96.31	3.441%	$99.624	$99.62	$99.60	$99.60
Purchase #2	$116.50	7.473%	$125.206	$125.21	$125.20	$125.20
Purchase #3	$29.46	7.191%	$31.5785	$31.58	$31.60	$31.60
Purchase #4	$71.53	11.664%	$79.8733	$79.87	$79.85	$79.90
Purchase #5	$64.74	11.458%	$72.1579	$72.16	$72.15	$72.20
Purchase #6	$74.75	10.131%	$82.3229	$82.32	$82.30	$82.30
Purchase #7	$210.53	10.542%	$232.7241	$232.72	$232.70	$232.70
7 purchase totals =	$663.82		$723.4867	$723.48	$723.40	$723.50