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	$102.56	6.210%	$108.929	$108.93	$108.95	$108.90
Purchase #2	$129.54	11.629%	$144.6042	$144.60	$144.60	$144.60
Purchase #3	$31.26	13.847%	$35.5886	$35.59	$35.60	$35.60
Purchase #4	$77.28	12.448%	$86.8998	$86.90	$86.90	$86.90
Purchase #5	$133.53	10.592%	$147.6735	$147.67	$147.65	$147.70
Purchase #6	$225.79	3.303%	$233.2478	$233.25	$233.25	$233.20
Purchase #7	$236.84	3.399%	$244.8902	$244.89	$244.90	$244.90
7 purchase totals =	$936.80		$1,001.8331	$1,001.83	$1,001.85	$1,001.80