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	$231.40	6.118%	$245.5571	$245.56	$245.55	$245.60
Purchase #2	$172.29	10.867%	$191.0128	$191.01	$191.00	$191.00
Purchase #3	$151.66	13.313%	$171.8505	$171.85	$171.85	$171.90
Purchase #4	$233.89	4.137%	$243.566	$243.57	$243.55	$243.60
Purchase #5	$63.27	6.264%	$67.2332	$67.23	$67.25	$67.20
Purchase #6	$202.55	4.333%	$211.3265	$211.33	$211.35	$211.30
Purchase #7	$243.63	12.624%	$274.3859	$274.39	$274.40	$274.40
7 purchase totals =	$1,298.69		$1,404.9320	$1,404.94	$1,404.95	$1,405.00