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	$146.76	9.118%	$160.1416	$160.14	$160.15	$160.10
Purchase #2	$113.35	9.513%	$124.133	$124.13	$124.15	$124.10
Purchase #3	$240.78	5.640%	$254.36	$254.36	$254.35	$254.40
Purchase #4	$76.79	10.870%	$85.1371	$85.14	$85.15	$85.10
Purchase #5	$150.72	12.853%	$170.092	$170.09	$170.10	$170.10
Purchase #6	$145.90	3.212%	$150.5863	$150.59	$150.60	$150.60
Purchase #7	$49.79	5.573%	$52.5648	$52.56	$52.55	$52.60
7 purchase totals =	$924.09		$997.0148	$997.01	$997.05	$997.00