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	$17.54	9.791%	$19.2573	$19.26	$19.25	$19.30
Purchase #2	$124.59	12.401%	$140.0404	$140.04	$140.05	$140.00
Purchase #3	$230.34	10.840%	$255.3089	$255.31	$255.30	$255.30
Purchase #4	$204.27	12.320%	$229.4361	$229.44	$229.45	$229.40
Purchase #5	$233.83	9.606%	$256.2917	$256.29	$256.30	$256.30
Purchase #6	$100.61	8.819%	$109.4828	$109.48	$109.50	$109.50
Purchase #7	$196.32	3.230%	$202.6611	$202.66	$202.65	$202.70
7 purchase totals =	$1,107.50		$1,212.4783	$1,212.48	$1,212.50	$1,212.50