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	$123.80	3.141%	$127.6886	$127.69	$127.70	$127.70
Purchase #2	$137.53	8.176%	$148.7745	$148.77	$148.75	$148.80
Purchase #3	$146.29	3.407%	$151.2741	$151.27	$151.25	$151.30
Purchase #4	$65.68	10.803%	$72.7754	$72.78	$72.80	$72.80
Purchase #5	$86.30	11.145%	$95.9181	$95.92	$95.90	$95.90
Purchase #6	$245.36	8.704%	$266.7161	$266.72	$266.70	$266.70
Purchase #7	$167.87	8.444%	$182.0449	$182.04	$182.05	$182.00
7 purchase totals =	$972.83		$1,045.1917	$1,045.19	$1,045.15	$1,045.20