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	$62.89	4.487%	$65.7119	$65.71	$65.70	$65.70
Purchase #2	$103.38	11.765%	$115.5427	$115.54	$115.55	$115.50
Purchase #3	$180.75	4.353%	$188.618	$188.62	$188.60	$188.60
Purchase #4	$115.83	10.477%	$127.9655	$127.97	$127.95	$128.00
Purchase #5	$29.56	11.444%	$32.9428	$32.94	$32.95	$32.90
Purchase #6	$85.78	9.399%	$93.8425	$93.84	$93.85	$93.80
Purchase #7	$98.97	13.436%	$112.2676	$112.27	$112.25	$112.30
7 purchase totals =	$677.16		$736.8910	$736.89	$736.85	$736.80