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	$130.57	13.357%	$148.0102	$148.01	$148.00	$148.00
Purchase #2	$62.71	9.244%	$68.5069	$68.51	$68.50	$68.50
Purchase #3	$207.89	5.116%	$218.5257	$218.53	$218.55	$218.50
Purchase #4	$48.31	4.441%	$50.4554	$50.46	$50.45	$50.50
Purchase #5	$233.54	7.414%	$250.8547	$250.85	$250.85	$250.90
Purchase #6	$50.75	3.238%	$52.3933	$52.39	$52.40	$52.40
Purchase #7	$198.78	12.404%	$223.4367	$223.44	$223.45	$223.40
7 purchase totals =	$932.55		$1,012.1829	$1,012.19	$1,012.20	$1,012.20