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	$164.33	6.372%	$174.8011	$174.80	$174.80	$174.80
Purchase #2	$208.82	7.176%	$223.8049	$223.80	$223.80	$223.80
Purchase #3	$41.38	5.245%	$43.5504	$43.55	$43.55	$43.60
Purchase #4	$99.95	5.371%	$105.3183	$105.32	$105.30	$105.30
Purchase #5	$154.96	3.190%	$159.9032	$159.90	$159.90	$159.90
Purchase #6	$245.76	5.187%	$258.5076	$258.51	$258.50	$258.50
Purchase #7	$56.81	12.616%	$63.9771	$63.98	$64.00	$64.00
7 purchase totals =	$972.01		$1,029.8626	$1,029.86	$1,029.85	$1,029.90