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	$151.80	3.103%	$156.5104	$156.51	$156.50	$156.50
Purchase #2	$72.64	7.873%	$78.3589	$78.36	$78.35	$78.40
Purchase #3	$92.63	13.620%	$105.2462	$105.25	$105.25	$105.20
Purchase #4	$48.31	3.766%	$50.1294	$50.13	$50.15	$50.10
Purchase #5	$234.87	10.310%	$259.0851	$259.09	$259.10	$259.10
Purchase #6	$222.94	12.732%	$251.3247	$251.32	$251.30	$251.30
Purchase #7	$175.29	5.377%	$184.7153	$184.72	$184.70	$184.70
7 purchase totals =	$998.48		$1,085.3700	$1,085.38	$1,085.35	$1,085.30