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	$180.73	9.152%	$197.2704	$197.27	$197.25	$197.30
Purchase #2	$119.92	6.627%	$127.8671	$127.87	$127.85	$127.90
Purchase #3	$64.46	4.511%	$67.3678	$67.37	$67.35	$67.40
Purchase #4	$30.56	9.484%	$33.4583	$33.46	$33.45	$33.50
Purchase #5	$23.31	4.223%	$24.2944	$24.29	$24.30	$24.30
Purchase #6	$67.80	13.579%	$77.0066	$77.01	$77.00	$77.00
Purchase #7	$168.77	8.331%	$182.8302	$182.83	$182.85	$182.80
7 purchase totals =	$655.55		$710.0948	$710.10	$710.05	$710.20