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	$243.74	5.597%	$257.3821	$257.38	$257.40	$257.40
Purchase #2	$173.59	3.314%	$179.3428	$179.34	$179.35	$179.30
Purchase #3	$51.54	5.338%	$54.2912	$54.29	$54.30	$54.30
Purchase #4	$230.66	7.370%	$247.6596	$247.66	$247.65	$247.70
Purchase #5	$31.75	11.321%	$35.3444	$35.34	$35.35	$35.30
Purchase #6	$190.80	3.151%	$196.8121	$196.81	$196.80	$196.80
Purchase #7	$67.25	10.138%	$74.0678	$74.07	$74.05	$74.10
7 purchase totals =	$989.33		$1,044.9000	$1,044.89	$1,044.90	$1,044.90