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	$98.48	11.585%	$109.8889	$109.89	$109.90	$109.90
Purchase #2	$149.91	13.503%	$170.1523	$170.15	$170.15	$170.20
Purchase #3	$58.42	4.283%	$60.9221	$60.92	$60.90	$60.90
Purchase #4	$73.92	12.760%	$83.3522	$83.35	$83.35	$83.40
Purchase #5	$185.66	13.851%	$211.3758	$211.38	$211.40	$211.40
Purchase #6	$32.92	13.235%	$37.277	$37.28	$37.30	$37.30
Purchase #7	$248.33	5.751%	$262.6115	$262.61	$262.60	$262.60
7 purchase totals =	$847.64		$935.5798	$935.58	$935.60	$935.70