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	$202.51	10.388%	$223.5467	$223.55	$223.55	$223.50
Purchase #2	$58.82	10.320%	$64.8902	$64.89	$64.90	$64.90
Purchase #3	$150.96	11.683%	$168.5967	$168.60	$168.60	$168.60
Purchase #4	$216.44	7.751%	$233.2163	$233.22	$233.20	$233.20
Purchase #5	$57.26	3.250%	$59.121	$59.12	$59.10	$59.10
Purchase #6	$60.99	12.498%	$68.6125	$68.61	$68.60	$68.60
Purchase #7	$47.74	4.452%	$49.8654	$49.87	$49.85	$49.90
7 purchase totals =	$794.72		$867.8488	$867.86	$867.80	$867.80