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	$138.80	4.797%	$145.4582	$145.46	$145.45	$145.50
Purchase #2	$214.68	3.556%	$222.314	$222.31	$222.30	$222.30
Purchase #3	$199.98	6.652%	$213.2827	$213.28	$213.30	$213.30
Purchase #4	$141.61	4.223%	$147.5902	$147.59	$147.60	$147.60
Purchase #5	$147.73	9.693%	$162.0495	$162.05	$162.05	$162.00
Purchase #6	$72.90	9.667%	$79.9472	$79.95	$79.95	$79.90
Purchase #7	$118.26	8.202%	$127.9597	$127.96	$127.95	$128.00
7 purchase totals =	$1,033.96		$1,098.6015	$1,098.60	$1,098.60	$1,098.60