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	$7.31	4.356%	$7.6284	$7.63	$7.65	$7.60
Purchase #2	$224.94	13.203%	$254.6388	$254.64	$254.65	$254.60
Purchase #3	$95.43	4.301%	$99.5344	$99.53	$99.55	$99.50
Purchase #4	$202.36	4.650%	$211.7697	$211.77	$211.75	$211.80
Purchase #5	$164.57	6.703%	$175.6011	$175.60	$175.60	$175.60
Purchase #6	$199.42	10.382%	$220.1238	$220.12	$220.10	$220.10
Purchase #7	$80.39	11.521%	$89.6517	$89.65	$89.65	$89.70
7 purchase totals =	$974.42		$1,058.9479	$1,058.94	$1,058.95	$1,058.90