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	$43.31	10.404%	$47.816	$47.82	$47.80	$47.80
Purchase #2	$247.89	12.769%	$279.5431	$279.54	$279.55	$279.50
Purchase #3	$197.84	4.727%	$207.1919	$207.19	$207.20	$207.20
Purchase #4	$128.74	6.431%	$137.0193	$137.02	$137.00	$137.00
Purchase #5	$96.50	9.409%	$105.5797	$105.58	$105.60	$105.60
Purchase #6	$168.51	3.769%	$174.8611	$174.86	$174.85	$174.90
Purchase #7	$97.77	11.621%	$109.1319	$109.13	$109.15	$109.10
7 purchase totals =	$980.56		$1,061.1430	$1,061.14	$1,061.15	$1,061.10