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	$83.49	5.425%	$88.0193	$88.02	$88.00	$88.00
Purchase #2	$74.36	5.340%	$78.3308	$78.33	$78.35	$78.30
Purchase #3	$111.57	5.794%	$118.0344	$118.03	$118.05	$118.00
Purchase #4	$129.89	13.418%	$147.3186	$147.32	$147.30	$147.30
Purchase #5	$49.81	5.278%	$52.439	$52.44	$52.45	$52.40
Purchase #6	$223.95	10.711%	$247.9373	$247.94	$247.95	$247.90
Purchase #7	$51.62	11.369%	$57.4887	$57.49	$57.50	$57.50
7 purchase totals =	$724.69		$789.5681	$789.57	$789.60	$789.40