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	$185.60	13.471%	$210.6022	$210.60	$210.60	$210.60
Purchase #2	$146.37	8.632%	$159.0047	$159.00	$159.00	$159.00
Purchase #3	$17.63	3.858%	$18.3102	$18.31	$18.30	$18.30
Purchase #4	$6.82	3.477%	$7.0571	$7.06	$7.05	$7.10
Purchase #5	$156.49	3.518%	$161.9953	$162.00	$162.00	$162.00
Purchase #6	$222.85	12.324%	$250.314	$250.31	$250.30	$250.30
Purchase #7	$230.63	12.347%	$259.1059	$259.11	$259.10	$259.10
7 purchase totals =	$966.39		$1,066.3894	$1,066.39	$1,066.35	$1,066.40