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	$189.58	10.135%	$208.7939	$208.79	$208.80	$208.80
Purchase #2	$89.55	10.786%	$99.2089	$99.21	$99.20	$99.20
Purchase #3	$22.40	11.180%	$24.9043	$24.90	$24.90	$24.90
Purchase #4	$132.40	3.389%	$136.887	$136.89	$136.90	$136.90
Purchase #5	$51.61	9.428%	$56.4758	$56.48	$56.50	$56.50
Purchase #6	$156.30	11.534%	$174.3276	$174.33	$174.35	$174.30
Purchase #7	$196.44	8.721%	$213.5715	$213.57	$213.55	$213.60
7 purchase totals =	$838.28		$914.1690	$914.17	$914.20	$914.20