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	$191.60	7.594%	$206.1501	$206.15	$206.15	$206.20
Purchase #2	$57.51	4.147%	$59.8949	$59.89	$59.90	$59.90
Purchase #3	$206.33	8.497%	$223.8619	$223.86	$223.85	$223.90
Purchase #4	$248.25	6.499%	$264.3838	$264.38	$264.40	$264.40
Purchase #5	$158.39	5.372%	$166.8987	$166.90	$166.90	$166.90
Purchase #6	$162.95	3.126%	$168.0438	$168.04	$168.05	$168.00
Purchase #7	$13.36	8.864%	$14.5442	$14.54	$14.55	$14.50
7 purchase totals =	$1,038.39		$1,103.7774	$1,103.76	$1,103.80	$1,103.80