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	$91.53	4.604%	$95.744	$95.74	$95.75	$95.70
Purchase #2	$87.83	12.284%	$98.619	$98.62	$98.60	$98.60
Purchase #3	$215.76	7.122%	$231.1264	$231.13	$231.15	$231.10
Purchase #4	$28.60	12.740%	$32.2436	$32.24	$32.25	$32.20
Purchase #5	$104.28	6.796%	$111.3669	$111.37	$111.35	$111.40
Purchase #6	$13.87	11.822%	$15.5097	$15.51	$15.50	$15.50
Purchase #7	$183.35	4.803%	$192.1563	$192.16	$192.15	$192.20
7 purchase totals =	$725.22		$776.7659	$776.77	$776.75	$776.70