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	$144.64	4.780%	$151.5538	$151.55	$151.55	$151.60
Purchase #2	$70.67	12.269%	$79.3405	$79.34	$79.35	$79.30
Purchase #3	$223.93	12.611%	$252.1698	$252.17	$252.15	$252.20
Purchase #4	$201.79	10.168%	$222.308	$222.31	$222.30	$222.30
Purchase #5	$186.55	3.872%	$193.7732	$193.77	$193.75	$193.80
Purchase #6	$40.30	11.871%	$45.084	$45.08	$45.10	$45.10
Purchase #7	$141.40	7.725%	$152.3232	$152.32	$152.30	$152.30
7 purchase totals =	$1,009.28		$1,096.5525	$1,096.54	$1,096.50	$1,096.60