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	$92.77	9.250%	$101.3512	$101.35	$101.35	$101.40
Purchase #2	$157.44	10.605%	$174.1365	$174.14	$174.15	$174.10
Purchase #3	$105.25	5.655%	$111.2019	$111.20	$111.20	$111.20
Purchase #4	$236.93	5.270%	$249.4162	$249.42	$249.40	$249.40
Purchase #5	$237.45	12.872%	$268.0146	$268.01	$268.00	$268.00
Purchase #6	$75.45	11.184%	$83.8883	$83.89	$83.90	$83.90
Purchase #7	$222.79	5.300%	$234.5979	$234.60	$234.60	$234.60
7 purchase totals =	$1,128.08		$1,222.6066	$1,222.61	$1,222.60	$1,222.60