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	$141.78	3.204%	$146.3226	$146.32	$146.30	$146.30
Purchase #2	$54.47	3.292%	$56.2632	$56.26	$56.25	$56.30
Purchase #3	$222.63	9.159%	$243.0207	$243.02	$243.00	$243.00
Purchase #4	$60.87	8.298%	$65.921	$65.92	$65.90	$65.90
Purchase #5	$217.56	5.571%	$229.6803	$229.68	$229.70	$229.70
Purchase #6	$113.70	8.713%	$123.6067	$123.61	$123.60	$123.60
Purchase #7	$190.34	11.700%	$212.6098	$212.61	$212.60	$212.60
7 purchase totals =	$1,001.35		$1,077.4243	$1,077.42	$1,077.35	$1,077.40