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	$125.85	6.393%	$133.8956	$133.90	$133.90	$133.90
Purchase #2	$12.43	3.664%	$12.8854	$12.89	$12.90	$12.90
Purchase #3	$202.33	4.556%	$211.5482	$211.55	$211.55	$211.50
Purchase #4	$100.26	3.180%	$103.4483	$103.45	$103.45	$103.40
Purchase #5	$85.75	9.690%	$94.0592	$94.06	$94.05	$94.10
Purchase #6	$51.35	11.874%	$57.4473	$57.45	$57.45	$57.40
Purchase #7	$231.70	3.711%	$240.2984	$240.30	$240.30	$240.30
7 purchase totals =	$809.67		$853.5824	$853.60	$853.60	$853.50