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	$109.85	6.256%	$116.7222	$116.72	$116.70	$116.70
Purchase #2	$172.87	6.108%	$183.4289	$183.43	$183.45	$183.40
Purchase #3	$243.92	12.137%	$273.5246	$273.52	$273.50	$273.50
Purchase #4	$232.43	9.344%	$254.1483	$254.15	$254.15	$254.10
Purchase #5	$207.59	7.660%	$223.4914	$223.49	$223.50	$223.50
Purchase #6	$201.59	7.343%	$216.3928	$216.39	$216.40	$216.40
Purchase #7	$190.36	3.278%	$196.6	$196.60	$196.60	$196.60
7 purchase totals =	$1,358.61		$1,464.3082	$1,464.30	$1,464.30	$1,464.20