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	$95.37	10.623%	$105.5012	$105.50	$105.50	$105.50
Purchase #2	$190.85	9.358%	$208.7097	$208.71	$208.70	$208.70
Purchase #3	$128.86	3.798%	$133.7541	$133.75	$133.75	$133.80
Purchase #4	$160.53	3.115%	$165.5305	$165.53	$165.55	$165.50
Purchase #5	$158.56	8.300%	$171.7205	$171.72	$171.70	$171.70
Purchase #6	$89.81	7.708%	$96.7326	$96.73	$96.75	$96.70
Purchase #7	$139.73	3.813%	$145.0579	$145.06	$145.05	$145.10
7 purchase totals =	$963.71		$1,027.0065	$1,027.00	$1,027.00	$1,027.00