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	$159.98	4.555%	$167.2671	$167.27	$167.25	$167.30
Purchase #2	$165.81	8.646%	$180.1459	$180.15	$180.15	$180.10
Purchase #3	$151.69	3.322%	$156.7291	$156.73	$156.75	$156.70
Purchase #4	$148.87	6.251%	$158.1759	$158.18	$158.20	$158.20
Purchase #5	$34.54	8.590%	$37.507	$37.51	$37.50	$37.50
Purchase #6	$41.80	8.544%	$45.3714	$45.37	$45.35	$45.40
Purchase #7	$72.52	7.791%	$78.17	$78.17	$78.15	$78.20
7 purchase totals =	$775.21		$823.3664	$823.38	$823.35	$823.40