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	$65.33	8.430%	$70.8373	$70.84	$70.85	$70.80
Purchase #2	$82.70	4.188%	$86.1635	$86.16	$86.15	$86.20
Purchase #3	$18.83	11.374%	$20.9717	$20.97	$20.95	$21.00
Purchase #4	$86.32	7.219%	$92.5514	$92.55	$92.55	$92.60
Purchase #5	$54.50	8.507%	$59.1363	$59.14	$59.15	$59.10
Purchase #6	$72.50	12.716%	$81.7191	$81.72	$81.70	$81.70
Purchase #7	$55.28	5.381%	$58.2546	$58.25	$58.25	$58.30
7 purchase totals =	$435.46		$469.6339	$469.63	$469.60	$469.70