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	$120.53	7.103%	$129.0912	$129.09	$129.10	$129.10
Purchase #2	$53.47	7.169%	$57.3033	$57.30	$57.30	$57.30
Purchase #3	$213.48	4.348%	$222.7621	$222.76	$222.75	$222.80
Purchase #4	$86.27	3.330%	$89.1428	$89.14	$89.15	$89.10
Purchase #5	$115.62	13.589%	$131.3316	$131.33	$131.35	$131.30
Purchase #6	$99.50	10.522%	$109.9694	$109.97	$109.95	$110.00
Purchase #7	$144.29	12.403%	$162.1863	$162.19	$162.20	$162.20
7 purchase totals =	$833.16		$901.7867	$901.78	$901.80	$901.80