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	$69.67	5.517%	$73.5137	$73.51	$73.50	$73.50
Purchase #2	$40.46	12.385%	$45.471	$45.47	$45.45	$45.50
Purchase #3	$233.27	4.702%	$244.2384	$244.24	$244.25	$244.20
Purchase #4	$79.80	4.475%	$83.3711	$83.37	$83.35	$83.40
Purchase #5	$38.45	11.487%	$42.8668	$42.87	$42.85	$42.90
Purchase #6	$118.87	10.655%	$131.5356	$131.54	$131.55	$131.50
Purchase #7	$205.62	11.705%	$229.6878	$229.69	$229.70	$229.70
7 purchase totals =	$786.14		$850.6844	$850.69	$850.65	$850.70