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	$88.54	9.554%	$96.9991	$97.00	$97.00	$97.00
Purchase #2	$156.44	10.512%	$172.885	$172.89	$172.90	$172.90
Purchase #3	$134.62	10.216%	$148.3728	$148.37	$148.35	$148.40
Purchase #4	$128.77	11.341%	$143.3738	$143.37	$143.35	$143.40
Purchase #5	$145.34	8.132%	$157.159	$157.16	$157.15	$157.20
Purchase #6	$149.41	12.191%	$167.6246	$167.62	$167.60	$167.60
Purchase #7	$148.72	10.372%	$164.1452	$164.15	$164.15	$164.10
7 purchase totals =	$951.84		$1,050.5595	$1,050.56	$1,050.50	$1,050.60