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	$205.98	6.504%	$219.3769	$219.38	$219.40	$219.40
Purchase #2	$121.45	6.370%	$129.1864	$129.19	$129.20	$129.20
Purchase #3	$148.26	13.507%	$168.2855	$168.29	$168.30	$168.30
Purchase #4	$88.91	11.801%	$99.4023	$99.40	$99.40	$99.40
Purchase #5	$146.33	12.423%	$164.5086	$164.51	$164.50	$164.50
Purchase #6	$59.61	8.283%	$64.5475	$64.55	$64.55	$64.50
Purchase #7	$171.32	8.665%	$186.1649	$186.16	$186.15	$186.20
7 purchase totals =	$941.86		$1,031.4721	$1,031.48	$1,031.50	$1,031.50