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	$89.28	10.766%	$98.8919	$98.89	$98.90	$98.90
Purchase #2	$232.43	5.112%	$244.3118	$244.31	$244.30	$244.30
Purchase #3	$57.30	5.140%	$60.2452	$60.25	$60.25	$60.20
Purchase #4	$250.65	12.865%	$282.8961	$282.90	$282.90	$282.90
Purchase #5	$212.69	5.232%	$223.8179	$223.82	$223.80	$223.80
Purchase #6	$206.78	9.331%	$226.0746	$226.07	$226.05	$226.10
Purchase #7	$246.59	9.647%	$270.3785	$270.38	$270.40	$270.40
7 purchase totals =	$1,295.72		$1,406.6160	$1,406.62	$1,406.60	$1,406.60