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	$222.42	5.566%	$234.7999	$234.80	$234.80	$234.80
Purchase #2	$174.56	3.113%	$179.9941	$179.99	$180.00	$180.00
Purchase #3	$189.72	11.648%	$211.8186	$211.82	$211.80	$211.80
Purchase #4	$182.59	4.165%	$190.1949	$190.19	$190.20	$190.20
Purchase #5	$55.31	12.593%	$62.2752	$62.28	$62.30	$62.30
Purchase #6	$217.72	10.593%	$240.7831	$240.78	$240.80	$240.80
Purchase #7	$46.31	4.602%	$48.4412	$48.44	$48.45	$48.40
7 purchase totals =	$1,088.63		$1,168.3070	$1,168.30	$1,168.35	$1,168.30