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	$63.44	11.823%	$70.9405	$70.94	$70.95	$70.90
Purchase #2	$164.74	4.401%	$171.9902	$171.99	$172.00	$172.00
Purchase #3	$17.34	4.364%	$18.0967	$18.10	$18.10	$18.10
Purchase #4	$239.32	10.432%	$264.2859	$264.29	$264.30	$264.30
Purchase #5	$87.50	13.721%	$99.5059	$99.51	$99.50	$99.50
Purchase #6	$247.46	10.539%	$273.5398	$273.54	$273.55	$273.50
Purchase #7	$18.66	6.435%	$19.8608	$19.86	$19.85	$19.90
7 purchase totals =	$838.46		$918.2198	$918.23	$918.25	$918.20