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	$43.86	6.861%	$46.8692	$46.87	$46.85	$46.90
Purchase #2	$171.83	8.525%	$186.4785	$186.48	$186.50	$186.50
Purchase #3	$165.97	7.526%	$178.4609	$178.46	$178.45	$178.50
Purchase #4	$138.80	8.864%	$151.1032	$151.10	$151.10	$151.10
Purchase #5	$135.53	9.530%	$148.446	$148.45	$148.45	$148.40
Purchase #6	$30.27	9.778%	$33.2298	$33.23	$33.25	$33.20
Purchase #7	$250.44	6.577%	$266.9114	$266.91	$266.90	$266.90
7 purchase totals =	$936.70		$1,011.4990	$1,011.50	$1,011.50	$1,011.50