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	$184.59	12.424%	$207.5235	$207.52	$207.50	$207.50
Purchase #2	$185.36	10.675%	$205.1472	$205.15	$205.15	$205.10
Purchase #3	$119.52	9.316%	$130.6545	$130.65	$130.65	$130.70
Purchase #4	$30.38	3.387%	$31.409	$31.41	$31.40	$31.40
Purchase #5	$148.74	5.205%	$156.4819	$156.48	$156.50	$156.50
Purchase #6	$123.47	6.516%	$131.5153	$131.52	$131.50	$131.50
Purchase #7	$163.72	12.428%	$184.0671	$184.07	$184.05	$184.10
7 purchase totals =	$955.78		$1,046.7985	$1,046.80	$1,046.75	$1,046.80