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	$250.40	5.395%	$263.9091	$263.91	$263.90	$263.90
Purchase #2	$102.65	11.826%	$114.7894	$114.79	$114.80	$114.80
Purchase #3	$50.75	7.607%	$54.6106	$54.61	$54.60	$54.60
Purchase #4	$108.89	4.872%	$114.1951	$114.20	$114.20	$114.20
Purchase #5	$160.40	5.131%	$168.6301	$168.63	$168.65	$168.60
Purchase #6	$91.95	13.854%	$104.6888	$104.69	$104.70	$104.70
Purchase #7	$231.96	13.695%	$263.7269	$263.73	$263.75	$263.70
7 purchase totals =	$997.00		$1,084.5500	$1,084.56	$1,084.60	$1,084.50