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	$179.61	4.431%	$187.5685	$187.57	$187.55	$187.60
Purchase #2	$127.29	11.528%	$141.964	$141.96	$141.95	$142.00
Purchase #3	$197.25	11.419%	$219.774	$219.77	$219.75	$219.80
Purchase #4	$19.48	4.541%	$20.3646	$20.36	$20.35	$20.40
Purchase #5	$105.90	9.738%	$116.2125	$116.21	$116.20	$116.20
Purchase #6	$147.27	3.235%	$152.0342	$152.03	$152.05	$152.00
Purchase #7	$148.89	6.612%	$158.7346	$158.73	$158.75	$158.70
7 purchase totals =	$925.69		$996.6524	$996.63	$996.60	$996.70