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	$170.96	6.436%	$181.963	$181.96	$181.95	$182.00
Purchase #2	$229.69	7.702%	$247.3807	$247.38	$247.40	$247.40
Purchase #3	$109.44	6.145%	$116.1651	$116.17	$116.15	$116.20
Purchase #4	$155.78	6.457%	$165.8387	$165.84	$165.85	$165.80
Purchase #5	$131.88	9.822%	$144.8333	$144.83	$144.85	$144.80
Purchase #6	$48.73	13.153%	$55.1395	$55.14	$55.15	$55.10
Purchase #7	$84.93	11.216%	$94.4557	$94.46	$94.45	$94.50
7 purchase totals =	$931.41		$1,005.7760	$1,005.78	$1,005.80	$1,005.80