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	$182.27	10.709%	$201.7893	$201.79	$201.80	$201.80
Purchase #2	$210.95	5.384%	$222.3075	$222.31	$222.30	$222.30
Purchase #3	$99.66	11.825%	$111.4448	$111.44	$111.45	$111.40
Purchase #4	$134.38	5.589%	$141.8905	$141.89	$141.90	$141.90
Purchase #5	$230.66	13.231%	$261.1786	$261.18	$261.20	$261.20
Purchase #6	$147.27	3.532%	$152.4716	$152.47	$152.45	$152.50
Purchase #7	$94.26	9.774%	$103.473	$103.47	$103.45	$103.50
7 purchase totals =	$1,099.45		$1,194.5553	$1,194.55	$1,194.55	$1,194.60