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	$123.39	5.241%	$129.8569	$129.86	$129.85	$129.90
Purchase #2	$58.53	7.840%	$63.1188	$63.12	$63.10	$63.10
Purchase #3	$139.93	9.504%	$153.2289	$153.23	$153.25	$153.20
Purchase #4	$228.59	7.404%	$245.5148	$245.51	$245.50	$245.50
Purchase #5	$233.36	8.557%	$253.3286	$253.33	$253.35	$253.30
Purchase #6	$100.45	9.369%	$109.8612	$109.86	$109.85	$109.90
Purchase #7	$75.30	4.167%	$78.4378	$78.44	$78.45	$78.40
7 purchase totals =	$959.55		$1,033.3470	$1,033.35	$1,033.35	$1,033.30