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	$67.35	13.227%	$76.2584	$76.26	$76.25	$76.30
Purchase #2	$185.53	10.419%	$204.8604	$204.86	$204.85	$204.90
Purchase #3	$130.27	9.110%	$142.1376	$142.14	$142.15	$142.10
Purchase #4	$174.77	5.732%	$184.7878	$184.79	$184.80	$184.80
Purchase #5	$170.25	13.140%	$192.6209	$192.62	$192.60	$192.60
Purchase #6	$238.91	13.783%	$271.839	$271.84	$271.85	$271.80
Purchase #7	$80.94	11.613%	$90.3396	$90.34	$90.35	$90.30
7 purchase totals =	$1,048.02		$1,162.8437	$1,162.85	$1,162.85	$1,162.80