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	$181.42	4.325%	$189.2664	$189.27	$189.25	$189.30
Purchase #2	$243.89	10.116%	$268.5619	$268.56	$268.55	$268.60
Purchase #3	$99.40	11.189%	$110.5219	$110.52	$110.50	$110.50
Purchase #4	$120.96	7.143%	$129.6002	$129.60	$129.60	$129.60
Purchase #5	$91.74	13.407%	$104.0396	$104.04	$104.05	$104.00
Purchase #6	$92.50	6.622%	$98.6254	$98.63	$98.65	$98.60
Purchase #7	$144.45	5.726%	$152.7212	$152.72	$152.70	$152.70
7 purchase totals =	$974.36		$1,053.3366	$1,053.34	$1,053.30	$1,053.30