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	$141.96	7.574%	$152.7121	$152.71	$152.70	$152.70
Purchase #2	$139.97	3.818%	$145.3141	$145.31	$145.30	$145.30
Purchase #3	$109.87	13.256%	$124.4344	$124.43	$124.45	$124.40
Purchase #4	$82.73	6.182%	$87.8444	$87.84	$87.85	$87.80
Purchase #5	$197.30	6.765%	$210.6473	$210.65	$210.65	$210.60
Purchase #6	$232.33	4.708%	$243.2681	$243.27	$243.25	$243.30
Purchase #7	$124.35	9.452%	$136.1036	$136.10	$136.10	$136.10
7 purchase totals =	$1,028.51		$1,100.3240	$1,100.31	$1,100.30	$1,100.20