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	$237.70	5.504%	$250.783	$250.78	$250.80	$250.80
Purchase #2	$62.92	6.854%	$67.2325	$67.23	$67.25	$67.20
Purchase #3	$94.76	5.872%	$100.3243	$100.32	$100.30	$100.30
Purchase #4	$50.76	5.834%	$53.7213	$53.72	$53.70	$53.70
Purchase #5	$205.65	9.380%	$224.94	$224.94	$224.95	$224.90
Purchase #6	$99.77	5.656%	$105.413	$105.41	$105.40	$105.40
Purchase #7	$13.72	3.193%	$14.1581	$14.16	$14.15	$14.20
7 purchase totals =	$765.28		$816.5722	$816.56	$816.55	$816.50