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	$81.92	11.550%	$91.3818	$91.38	$91.40	$91.40
Purchase #2	$22.48	7.294%	$24.1197	$24.12	$24.10	$24.10
Purchase #3	$100.78	3.135%	$103.9395	$103.94	$103.95	$103.90
Purchase #4	$185.88	10.246%	$204.9253	$204.93	$204.95	$204.90
Purchase #5	$37.30	8.600%	$40.5078	$40.51	$40.50	$40.50
Purchase #6	$42.33	9.583%	$46.3865	$46.39	$46.40	$46.40
Purchase #7	$167.96	8.644%	$182.4785	$182.48	$182.50	$182.50
7 purchase totals =	$638.65		$693.7391	$693.75	$693.80	$693.70