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	$28.48	3.498%	$29.4762	$29.48	$29.50	$29.50
Purchase #2	$59.72	12.576%	$67.2304	$67.23	$67.25	$67.20
Purchase #3	$243.73	12.139%	$273.3164	$273.32	$273.30	$273.30
Purchase #4	$58.93	12.718%	$66.4247	$66.42	$66.40	$66.40
Purchase #5	$129.86	5.436%	$136.9192	$136.92	$136.90	$136.90
Purchase #6	$129.45	11.455%	$144.2785	$144.28	$144.30	$144.30
Purchase #7	$216.87	8.470%	$235.2389	$235.24	$235.25	$235.20
7 purchase totals =	$867.04		$952.8843	$952.89	$952.90	$952.80