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	$163.95	3.440%	$169.5899	$169.59	$169.60	$169.60
Purchase #2	$53.28	12.508%	$59.9443	$59.94	$59.95	$59.90
Purchase #3	$183.50	9.170%	$200.327	$200.33	$200.35	$200.30
Purchase #4	$170.58	11.136%	$189.5758	$189.58	$189.60	$189.60
Purchase #5	$104.87	8.661%	$113.9528	$113.95	$113.95	$114.00
Purchase #6	$215.86	3.567%	$223.5597	$223.56	$223.55	$223.60
Purchase #7	$99.73	10.110%	$109.8127	$109.81	$109.80	$109.80
7 purchase totals =	$991.77		$1,066.7622	$1,066.76	$1,066.80	$1,066.80