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	$171.61	8.157%	$185.6082	$185.61	$185.60	$185.60
Purchase #2	$21.81	12.317%	$24.4963	$24.50	$24.50	$24.50
Purchase #3	$221.30	8.601%	$240.334	$240.33	$240.35	$240.30
Purchase #4	$207.26	7.374%	$222.5434	$222.54	$222.55	$222.50
Purchase #5	$50.48	3.228%	$52.1095	$52.11	$52.10	$52.10
Purchase #6	$53.73	13.525%	$60.997	$61.00	$61.00	$61.00
Purchase #7	$203.86	9.827%	$223.8933	$223.89	$223.90	$223.90
7 purchase totals =	$930.05		$1,009.9817	$1,009.98	$1,010.00	$1,009.90