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	$143.41	8.449%	$155.5267	$155.53	$155.55	$155.50
Purchase #2	$247.93	11.715%	$276.975	$276.98	$277.00	$277.00
Purchase #3	$75.64	7.835%	$81.5664	$81.57	$81.55	$81.60
Purchase #4	$99.56	4.433%	$103.9735	$103.97	$103.95	$104.00
Purchase #5	$108.86	7.830%	$117.3837	$117.38	$117.40	$117.40
Purchase #6	$131.77	9.793%	$144.6742	$144.67	$144.65	$144.70
Purchase #7	$113.96	12.194%	$127.8563	$127.86	$127.85	$127.90
7 purchase totals =	$921.13		$1,007.9558	$1,007.96	$1,007.95	$1,008.10