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	$210.57	3.244%	$217.4009	$217.40	$217.40	$217.40
Purchase #2	$189.76	4.763%	$198.7983	$198.80	$198.80	$198.80
Purchase #3	$227.93	6.481%	$242.7021	$242.70	$242.70	$242.70
Purchase #4	$96.76	7.717%	$104.227	$104.23	$104.25	$104.20
Purchase #5	$96.68	3.123%	$99.6993	$99.70	$99.70	$99.70
Purchase #6	$132.47	13.633%	$150.5296	$150.53	$150.55	$150.50
Purchase #7	$158.52	4.230%	$165.2254	$165.23	$165.25	$165.20
7 purchase totals =	$1,112.69		$1,178.5826	$1,178.59	$1,178.65	$1,178.50