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	$209.67	11.609%	$234.0106	$234.01	$234.00	$234.00
Purchase #2	$146.79	9.409%	$160.6015	$160.60	$160.60	$160.60
Purchase #3	$203.51	4.160%	$211.976	$211.98	$212.00	$212.00
Purchase #4	$171.91	4.215%	$179.156	$179.16	$179.15	$179.20
Purchase #5	$111.93	11.554%	$124.8624	$124.86	$124.85	$124.90
Purchase #6	$88.29	3.700%	$91.5567	$91.56	$91.55	$91.60
Purchase #7	$28.66	9.354%	$31.3409	$31.34	$31.35	$31.30
7 purchase totals =	$960.76		$1,033.5041	$1,033.51	$1,033.50	$1,033.60