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	$143.25	5.298%	$150.8394	$150.84	$150.85	$150.80
Purchase #2	$188.34	11.102%	$209.2495	$209.25	$209.25	$209.20
Purchase #3	$135.95	6.673%	$145.0219	$145.02	$145.00	$145.00
Purchase #4	$162.33	4.677%	$169.9222	$169.92	$169.90	$169.90
Purchase #5	$92.48	9.113%	$100.9077	$100.91	$100.90	$100.90
Purchase #6	$222.79	12.218%	$250.0105	$250.01	$250.00	$250.00
Purchase #7	$56.51	4.858%	$59.2553	$59.26	$59.25	$59.30
7 purchase totals =	$1,001.65		$1,085.2065	$1,085.21	$1,085.15	$1,085.10