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	$8.92	13.768%	$10.1481	$10.15	$10.15	$10.10
Purchase #2	$215.73	8.350%	$233.7435	$233.74	$233.75	$233.70
Purchase #3	$125.74	12.352%	$141.2714	$141.27	$141.25	$141.30
Purchase #4	$172.41	5.657%	$182.1632	$182.16	$182.15	$182.20
Purchase #5	$107.33	5.401%	$113.1269	$113.13	$113.15	$113.10
Purchase #6	$207.56	3.832%	$215.5137	$215.51	$215.50	$215.50
Purchase #7	$55.72	10.286%	$61.4514	$61.45	$61.45	$61.50
7 purchase totals =	$893.41		$957.4182	$957.41	$957.40	$957.40