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	$217.70	8.189%	$235.5275	$235.53	$235.55	$235.50
Purchase #2	$45.34	12.260%	$50.8987	$50.90	$50.90	$50.90
Purchase #3	$118.65	6.867%	$126.7977	$126.80	$126.80	$126.80
Purchase #4	$148.38	10.801%	$164.4065	$164.41	$164.40	$164.40
Purchase #5	$88.62	8.688%	$96.3193	$96.32	$96.30	$96.30
Purchase #6	$133.91	6.360%	$142.4267	$142.43	$142.45	$142.40
Purchase #7	$224.82	4.302%	$234.4918	$234.49	$234.50	$234.50
7 purchase totals =	$977.42		$1,050.8682	$1,050.88	$1,050.90	$1,050.80