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	$213.47	10.655%	$236.2152	$236.22	$236.20	$236.20
Purchase #2	$93.76	7.449%	$100.7442	$100.74	$100.75	$100.70
Purchase #3	$115.38	7.325%	$123.8316	$123.83	$123.85	$123.80
Purchase #4	$83.92	8.356%	$90.9324	$90.93	$90.95	$90.90
Purchase #5	$67.75	13.674%	$77.0141	$77.01	$77.00	$77.00
Purchase #6	$245.54	8.678%	$266.848	$266.85	$266.85	$266.80
Purchase #7	$99.60	9.399%	$108.9614	$108.96	$108.95	$109.00
7 purchase totals =	$919.42		$1,004.5469	$1,004.54	$1,004.55	$1,004.40