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	$121.80	4.831%	$127.6842	$127.68	$127.70	$127.70
Purchase #2	$173.44	3.872%	$180.1556	$180.16	$180.15	$180.20
Purchase #3	$192.79	8.627%	$209.422	$209.42	$209.40	$209.40
Purchase #4	$40.48	12.585%	$45.5744	$45.57	$45.55	$45.60
Purchase #5	$75.25	13.281%	$85.244	$85.24	$85.25	$85.20
Purchase #6	$50.77	7.503%	$54.5793	$54.58	$54.60	$54.60
Purchase #7	$57.65	12.720%	$64.9831	$64.98	$65.00	$65.00
7 purchase totals =	$712.18		$767.6426	$767.63	$767.65	$767.70