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	$110.57	3.510%	$114.451	$114.45	$114.45	$114.50
Purchase #2	$113.46	3.273%	$117.1735	$117.17	$117.15	$117.20
Purchase #3	$87.54	12.850%	$98.7889	$98.79	$98.80	$98.80
Purchase #4	$91.89	11.129%	$102.1164	$102.12	$102.10	$102.10
Purchase #5	$85.78	6.645%	$91.4801	$91.48	$91.50	$91.50
Purchase #6	$128.97	12.511%	$145.1054	$145.11	$145.10	$145.10
Purchase #7	$142.39	5.510%	$150.2357	$150.24	$150.25	$150.20
7 purchase totals =	$760.60		$819.3510	$819.36	$819.35	$819.40