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	$125.91	12.118%	$141.1678	$141.17	$141.15	$141.20
Purchase #2	$129.26	13.237%	$146.3701	$146.37	$146.35	$146.40
Purchase #3	$123.48	10.820%	$136.8405	$136.84	$136.85	$136.80
Purchase #4	$103.95	6.690%	$110.9043	$110.90	$110.90	$110.90
Purchase #5	$122.98	3.658%	$127.4786	$127.48	$127.50	$127.50
Purchase #6	$218.31	10.665%	$241.5928	$241.59	$241.60	$241.60
Purchase #7	$186.30	10.190%	$205.284	$205.28	$205.30	$205.30
7 purchase totals =	$1,010.19		$1,109.6381	$1,109.63	$1,109.65	$1,109.70