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	$159.87	6.106%	$169.6317	$169.63	$169.65	$169.60
Purchase #2	$81.97	11.473%	$91.3744	$91.37	$91.35	$91.40
Purchase #3	$156.39	9.507%	$171.258	$171.26	$171.25	$171.30
Purchase #4	$106.33	13.578%	$120.7675	$120.77	$120.75	$120.80
Purchase #5	$168.33	7.151%	$180.3673	$180.37	$180.35	$180.40
Purchase #6	$45.68	12.738%	$51.4987	$51.50	$51.50	$51.50
Purchase #7	$225.25	3.776%	$233.7554	$233.76	$233.75	$233.80
7 purchase totals =	$943.82		$1,018.6530	$1,018.66	$1,018.60	$1,018.80