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	$86.58	13.664%	$98.4103	$98.41	$98.40	$98.40
Purchase #2	$60.34	11.572%	$67.3225	$67.32	$67.30	$67.30
Purchase #3	$161.82	10.507%	$178.8224	$178.82	$178.80	$178.80
Purchase #4	$176.81	6.173%	$187.7245	$187.72	$187.70	$187.70
Purchase #5	$205.29	11.225%	$228.3338	$228.33	$228.35	$228.30
Purchase #6	$196.76	10.743%	$217.8979	$217.90	$217.90	$217.90
Purchase #7	$53.68	3.321%	$55.4627	$55.46	$55.45	$55.50
7 purchase totals =	$941.28		$1,033.9741	$1,033.96	$1,033.90	$1,033.90