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	$74.95	6.193%	$79.5917	$79.59	$79.60	$79.60
Purchase #2	$144.89	3.451%	$149.8902	$149.89	$149.90	$149.90
Purchase #3	$199.47	4.736%	$208.9169	$208.92	$208.90	$208.90
Purchase #4	$73.78	9.472%	$80.7684	$80.77	$80.75	$80.80
Purchase #5	$158.44	10.163%	$174.5423	$174.54	$174.55	$174.50
Purchase #6	$65.90	6.666%	$70.2929	$70.29	$70.30	$70.30
Purchase #7	$242.86	3.278%	$250.821	$250.82	$250.80	$250.80
7 purchase totals =	$960.29		$1,014.8234	$1,014.82	$1,014.80	$1,014.80