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	$78.49	3.623%	$81.3337	$81.33	$81.35	$81.30
Purchase #2	$86.96	3.633%	$90.1193	$90.12	$90.10	$90.10
Purchase #3	$86.62	13.368%	$98.1994	$98.20	$98.20	$98.20
Purchase #4	$215.75	3.638%	$223.599	$223.60	$223.60	$223.60
Purchase #5	$121.89	12.525%	$137.1567	$137.16	$137.15	$137.20
Purchase #6	$90.75	3.463%	$93.8927	$93.89	$93.90	$93.90
Purchase #7	$124.31	3.545%	$128.7168	$128.72	$128.70	$128.70
7 purchase totals =	$804.77		$853.0176	$853.02	$853.00	$853.00