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	$98.34	13.191%	$111.312	$111.31	$111.30	$111.30
Purchase #2	$237.47	13.116%	$268.6166	$268.62	$268.60	$268.60
Purchase #3	$200.45	13.564%	$227.639	$227.64	$227.65	$227.60
Purchase #4	$150.74	11.165%	$167.5701	$167.57	$167.55	$167.60
Purchase #5	$107.42	3.311%	$110.9767	$110.98	$111.00	$111.00
Purchase #6	$244.68	11.784%	$273.5131	$273.51	$273.50	$273.50
Purchase #7	$78.43	5.337%	$82.6158	$82.62	$82.60	$82.60
7 purchase totals =	$1,117.53		$1,242.2433	$1,242.25	$1,242.20	$1,242.20