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	$195.90	11.824%	$219.0632	$219.06	$219.05	$219.10
Purchase #2	$42.48	11.255%	$47.2611	$47.26	$47.25	$47.30
Purchase #3	$225.42	10.609%	$249.3348	$249.33	$249.35	$249.30
Purchase #4	$248.49	13.223%	$281.3478	$281.35	$281.35	$281.30
Purchase #5	$38.48	10.142%	$42.3826	$42.38	$42.40	$42.40
Purchase #6	$59.56	3.695%	$61.7607	$61.76	$61.75	$61.80
Purchase #7	$180.46	3.491%	$186.7599	$186.76	$186.75	$186.80
7 purchase totals =	$990.79		$1,087.9101	$1,087.90	$1,087.90	$1,088.00