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	$234.26	13.767%	$266.5106	$266.51	$266.50	$266.50
Purchase #2	$171.81	3.813%	$178.3611	$178.36	$178.35	$178.40
Purchase #3	$129.38	10.718%	$143.2469	$143.25	$143.25	$143.20
Purchase #4	$142.49	10.380%	$157.2805	$157.28	$157.30	$157.30
Purchase #5	$193.54	5.874%	$204.9085	$204.91	$204.90	$204.90
Purchase #6	$92.58	7.254%	$99.2958	$99.30	$99.30	$99.30
Purchase #7	$129.27	13.667%	$146.9373	$146.94	$146.95	$146.90
7 purchase totals =	$1,093.33		$1,196.5407	$1,196.55	$1,196.55	$1,196.50