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	$70.57	11.510%	$78.6926	$78.69	$78.70	$78.70
Purchase #2	$193.63	6.369%	$205.9623	$205.96	$205.95	$206.00
Purchase #3	$12.98	8.461%	$14.0782	$14.08	$14.10	$14.10
Purchase #4	$108.70	13.482%	$123.3549	$123.35	$123.35	$123.40
Purchase #5	$120.44	6.145%	$127.841	$127.84	$127.85	$127.80
Purchase #6	$211.69	6.398%	$225.2339	$225.23	$225.25	$225.20
Purchase #7	$172.60	7.588%	$185.6969	$185.70	$185.70	$185.70
7 purchase totals =	$890.61		$960.8598	$960.85	$960.90	$960.90