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	$53.25	9.458%	$58.2864	$58.29	$58.30	$58.30
Purchase #2	$99.26	9.764%	$108.9517	$108.95	$108.95	$109.00
Purchase #3	$35.95	3.862%	$37.3384	$37.34	$37.35	$37.30
Purchase #4	$160.86	9.322%	$175.8554	$175.86	$175.85	$175.90
Purchase #5	$154.89	3.119%	$159.721	$159.72	$159.70	$159.70
Purchase #6	$131.58	4.394%	$137.3616	$137.36	$137.35	$137.40
Purchase #7	$187.37	4.743%	$196.257	$196.26	$196.25	$196.30
7 purchase totals =	$823.16		$873.7715	$873.78	$873.75	$873.90