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	$151.50	11.790%	$169.3619	$169.36	$169.35	$169.40
Purchase #2	$85.49	7.562%	$91.9548	$91.95	$91.95	$92.00
Purchase #3	$223.41	12.252%	$250.7822	$250.78	$250.80	$250.80
Purchase #4	$31.31	4.250%	$32.6407	$32.64	$32.65	$32.60
Purchase #5	$129.85	12.274%	$145.7878	$145.79	$145.80	$145.80
Purchase #6	$213.72	4.350%	$223.0168	$223.02	$223.00	$223.00
Purchase #7	$153.76	9.661%	$168.6148	$168.61	$168.60	$168.60
7 purchase totals =	$989.04		$1,082.1590	$1,082.15	$1,082.15	$1,082.20