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	$144.55	8.179%	$156.3727	$156.37	$156.35	$156.40
Purchase #2	$18.28	3.427%	$18.9065	$18.91	$18.90	$18.90
Purchase #3	$136.88	3.699%	$141.9432	$141.94	$141.95	$141.90
Purchase #4	$73.30	6.428%	$78.0117	$78.01	$78.00	$78.00
Purchase #5	$197.29	7.455%	$211.998	$212.00	$212.00	$212.00
Purchase #6	$69.68	12.536%	$78.4151	$78.42	$78.40	$78.40
Purchase #7	$57.74	7.278%	$61.9423	$61.94	$61.95	$61.90
7 purchase totals =	$697.72		$747.5895	$747.59	$747.55	$747.50