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	$154.61	11.155%	$171.8567	$171.86	$171.85	$171.90
Purchase #2	$218.27	3.115%	$225.0691	$225.07	$225.05	$225.10
Purchase #3	$78.53	13.280%	$88.9588	$88.96	$88.95	$89.00
Purchase #4	$27.56	11.861%	$30.8289	$30.83	$30.85	$30.80
Purchase #5	$54.84	8.318%	$59.4016	$59.40	$59.40	$59.40
Purchase #6	$90.80	5.140%	$95.4671	$95.47	$95.45	$95.50
Purchase #7	$81.37	13.703%	$92.5201	$92.52	$92.50	$92.50
7 purchase totals =	$705.98		$764.1023	$764.11	$764.05	$764.20