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	$130.88	6.453%	$139.3257	$139.33	$139.35	$139.30
Purchase #2	$206.77	6.372%	$219.9454	$219.95	$219.95	$219.90
Purchase #3	$170.40	11.224%	$189.5257	$189.53	$189.55	$189.50
Purchase #4	$184.59	6.163%	$195.9663	$195.97	$195.95	$196.00
Purchase #5	$24.80	13.601%	$28.173	$28.17	$28.15	$28.20
Purchase #6	$127.28	10.455%	$140.5871	$140.59	$140.60	$140.60
Purchase #7	$86.38	7.538%	$92.8913	$92.89	$92.90	$92.90
7 purchase totals =	$931.10		$1,006.4145	$1,006.43	$1,006.45	$1,006.40