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	$190.32	9.243%	$207.9113	$207.91	$207.90	$207.90
Purchase #2	$245.90	9.286%	$268.7343	$268.73	$268.75	$268.70
Purchase #3	$19.97	6.262%	$21.2205	$21.22	$21.20	$21.20
Purchase #4	$169.65	12.355%	$190.6103	$190.61	$190.60	$190.60
Purchase #5	$12.48	8.388%	$13.5268	$13.53	$13.55	$13.50
Purchase #6	$110.90	11.711%	$123.8875	$123.89	$123.90	$123.90
Purchase #7	$225.91	3.427%	$233.6519	$233.65	$233.65	$233.70
7 purchase totals =	$975.13		$1,059.5426	$1,059.54	$1,059.55	$1,059.50