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	$213.67	7.517%	$229.7316	$229.73	$229.75	$229.70
Purchase #2	$72.47	11.851%	$81.0584	$81.06	$81.05	$81.10
Purchase #3	$109.40	7.797%	$117.9299	$117.93	$117.95	$117.90
Purchase #4	$173.79	9.563%	$190.4095	$190.41	$190.40	$190.40
Purchase #5	$179.89	4.838%	$188.5931	$188.59	$188.60	$188.60
Purchase #6	$81.36	11.327%	$90.5756	$90.58	$90.60	$90.60
Purchase #7	$6.80	6.736%	$7.258	$7.26	$7.25	$7.30
7 purchase totals =	$837.38		$905.5561	$905.56	$905.60	$905.60