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	$92.89	7.119%	$99.5028	$99.50	$99.50	$99.50
Purchase #2	$70.81	4.449%	$73.9603	$73.96	$73.95	$74.00
Purchase #3	$63.99	4.710%	$67.0039	$67.00	$67.00	$67.00
Purchase #4	$67.43	7.816%	$72.7003	$72.70	$72.70	$72.70
Purchase #5	$204.27	12.381%	$229.5607	$229.56	$229.55	$229.60
Purchase #6	$41.97	11.459%	$46.7793	$46.78	$46.80	$46.80
Purchase #7	$192.95	11.736%	$215.5946	$215.59	$215.60	$215.60
7 purchase totals =	$734.31		$805.1019	$805.09	$805.10	$805.20