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	$210.95	10.655%	$233.4267	$233.43	$233.45	$233.40
Purchase #2	$47.56	9.148%	$51.9108	$51.91	$51.90	$51.90
Purchase #3	$170.40	8.228%	$184.4205	$184.42	$184.40	$184.40
Purchase #4	$215.80	5.557%	$227.792	$227.79	$227.80	$227.80
Purchase #5	$51.37	10.255%	$56.638	$56.64	$56.65	$56.60
Purchase #6	$85.70	11.614%	$95.6532	$95.65	$95.65	$95.70
Purchase #7	$204.89	5.710%	$216.5892	$216.59	$216.60	$216.60
7 purchase totals =	$986.67		$1,066.4304	$1,066.43	$1,066.45	$1,066.40