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	$220.29	4.861%	$230.9983	$231.00	$231.00	$231.00
Purchase #2	$123.45	8.351%	$133.7593	$133.76	$133.75	$133.80
Purchase #3	$6.91	10.634%	$7.6448	$7.64	$7.65	$7.60
Purchase #4	$66.71	9.279%	$72.9	$72.90	$72.90	$72.90
Purchase #5	$94.27	6.515%	$100.4117	$100.41	$100.40	$100.40
Purchase #6	$185.69	9.665%	$203.6369	$203.64	$203.65	$203.60
Purchase #7	$244.44	9.158%	$266.8258	$266.83	$266.85	$266.80
7 purchase totals =	$941.76		$1,016.1768	$1,016.18	$1,016.20	$1,016.10