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	$89.95	11.655%	$100.4337	$100.43	$100.45	$100.40
Purchase #2	$156.99	6.523%	$167.2305	$167.23	$167.25	$167.20
Purchase #3	$216.32	10.214%	$238.4149	$238.41	$238.40	$238.40
Purchase #4	$138.73	6.254%	$147.4062	$147.41	$147.40	$147.40
Purchase #5	$74.97	5.212%	$78.8774	$78.88	$78.90	$78.90
Purchase #6	$232.34	5.417%	$244.9259	$244.93	$244.95	$244.90
Purchase #7	$73.31	3.739%	$76.0511	$76.05	$76.05	$76.10
7 purchase totals =	$982.61		$1,053.3397	$1,053.34	$1,053.40	$1,053.30