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	$205.89	12.657%	$231.9495	$231.95	$231.95	$231.90
Purchase #2	$50.46	3.695%	$52.3245	$52.32	$52.30	$52.30
Purchase #3	$52.98	3.321%	$54.7395	$54.74	$54.75	$54.70
Purchase #4	$211.65	7.802%	$228.1629	$228.16	$228.15	$228.20
Purchase #5	$157.81	4.253%	$164.5217	$164.52	$164.50	$164.50
Purchase #6	$214.78	8.515%	$233.0685	$233.07	$233.05	$233.10
Purchase #7	$79.81	3.857%	$82.8883	$82.89	$82.90	$82.90
7 purchase totals =	$973.38		$1,047.6549	$1,047.65	$1,047.60	$1,047.60