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	$174.77	9.257%	$190.9485	$190.95	$190.95	$190.90
Purchase #2	$99.28	13.499%	$112.6818	$112.68	$112.70	$112.70
Purchase #3	$23.72	11.224%	$26.3823	$26.38	$26.40	$26.40
Purchase #4	$91.41	13.221%	$103.4953	$103.50	$103.50	$103.50
Purchase #5	$39.42	7.629%	$42.4274	$42.43	$42.45	$42.40
Purchase #6	$127.97	3.556%	$132.5206	$132.52	$132.50	$132.50
Purchase #7	$189.86	9.816%	$208.4967	$208.50	$208.50	$208.50
7 purchase totals =	$746.43		$816.9526	$816.96	$817.00	$816.90