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	$242.25	9.713%	$265.7797	$265.78	$265.80	$265.80
Purchase #2	$114.73	11.252%	$127.6394	$127.64	$127.65	$127.60
Purchase #3	$73.86	4.581%	$77.2435	$77.24	$77.25	$77.20
Purchase #4	$52.72	6.874%	$56.344	$56.34	$56.35	$56.30
Purchase #5	$36.25	8.772%	$39.4299	$39.43	$39.45	$39.40
Purchase #6	$31.33	8.261%	$33.9182	$33.92	$33.90	$33.90
Purchase #7	$148.40	3.288%	$153.2794	$153.28	$153.30	$153.30
7 purchase totals =	$699.54		$753.6341	$753.63	$753.70	$753.50