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	$168.30	10.814%	$186.5	$186.50	$186.50	$186.50
Purchase #2	$207.72	6.752%	$221.7453	$221.75	$221.75	$221.70
Purchase #3	$78.64	13.241%	$89.0527	$89.05	$89.05	$89.10
Purchase #4	$129.60	11.289%	$144.2305	$144.23	$144.25	$144.20
Purchase #5	$20.76	6.240%	$22.0554	$22.06	$22.05	$22.10
Purchase #6	$169.27	5.513%	$178.6019	$178.60	$178.60	$178.60
Purchase #7	$86.47	10.140%	$95.2381	$95.24	$95.25	$95.20
7 purchase totals =	$860.76		$937.4239	$937.43	$937.45	$937.40