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	$132.82	12.223%	$149.0546	$149.05	$149.05	$149.10
Purchase #2	$85.83	7.747%	$92.4793	$92.48	$92.50	$92.50
Purchase #3	$167.37	13.857%	$190.5625	$190.56	$190.55	$190.60
Purchase #4	$50.88	13.353%	$57.674	$57.67	$57.65	$57.70
Purchase #5	$96.51	4.771%	$101.1145	$101.11	$101.10	$101.10
Purchase #6	$29.57	6.838%	$31.592	$31.59	$31.60	$31.60
Purchase #7	$73.77	4.258%	$76.9111	$76.91	$76.90	$76.90
7 purchase totals =	$636.75		$699.3880	$699.37	$699.35	$699.50