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	$144.31	9.498%	$158.0166	$158.02	$158.00	$158.00
Purchase #2	$143.46	4.834%	$150.3949	$150.39	$150.40	$150.40
Purchase #3	$50.34	6.295%	$53.5089	$53.51	$53.50	$53.50
Purchase #4	$104.93	11.254%	$116.7388	$116.74	$116.75	$116.70
Purchase #5	$163.95	8.272%	$177.5119	$177.51	$177.50	$177.50
Purchase #6	$235.26	12.414%	$264.4652	$264.47	$264.45	$264.50
Purchase #7	$207.55	7.556%	$223.2325	$223.23	$223.25	$223.20
7 purchase totals =	$1,049.80		$1,143.8688	$1,143.87	$1,143.85	$1,143.80