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	$233.82	4.467%	$244.2647	$244.26	$244.25	$244.30
Purchase #2	$24.38	6.635%	$25.9976	$26.00	$26.00	$26.00
Purchase #3	$156.66	12.525%	$176.2817	$176.28	$176.30	$176.30
Purchase #4	$88.54	13.463%	$100.4601	$100.46	$100.45	$100.50
Purchase #5	$71.82	9.343%	$78.5301	$78.53	$78.55	$78.50
Purchase #6	$152.88	9.626%	$167.5962	$167.60	$167.60	$167.60
Purchase #7	$149.79	4.825%	$157.0174	$157.02	$157.00	$157.00
7 purchase totals =	$877.89		$950.1478	$950.15	$950.15	$950.20