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	$46.51	11.280%	$51.7563	$51.76	$51.75	$51.80
Purchase #2	$95.44	9.656%	$104.6557	$104.66	$104.65	$104.70
Purchase #3	$176.31	8.276%	$190.9014	$190.90	$190.90	$190.90
Purchase #4	$99.69	7.189%	$106.8567	$106.86	$106.85	$106.90
Purchase #5	$53.97	10.204%	$59.4771	$59.48	$59.50	$59.50
Purchase #6	$81.34	5.539%	$85.8454	$85.85	$85.85	$85.80
Purchase #7	$244.99	9.599%	$268.5066	$268.51	$268.50	$268.50
7 purchase totals =	$798.25		$867.9992	$868.02	$868.00	$868.10