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	$96.44	9.230%	$105.3414	$105.34	$105.35	$105.30
Purchase #2	$238.52	9.178%	$260.4114	$260.41	$260.40	$260.40
Purchase #3	$108.93	4.157%	$113.4582	$113.46	$113.45	$113.50
Purchase #4	$225.37	3.531%	$233.3278	$233.33	$233.35	$233.30
Purchase #5	$58.67	11.603%	$65.4775	$65.48	$65.50	$65.50
Purchase #6	$207.49	12.498%	$233.4221	$233.42	$233.40	$233.40
Purchase #7	$131.73	12.608%	$148.3385	$148.34	$148.35	$148.30
7 purchase totals =	$1,067.15		$1,159.7769	$1,159.78	$1,159.80	$1,159.70