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	$72.84	8.278%	$78.8697	$78.87	$78.85	$78.90
Purchase #2	$73.37	3.563%	$75.9842	$75.98	$76.00	$76.00
Purchase #3	$244.81	9.713%	$268.5884	$268.59	$268.60	$268.60
Purchase #4	$16.38	3.778%	$16.9988	$17.00	$17.00	$17.00
Purchase #5	$86.71	3.217%	$89.4995	$89.50	$89.50	$89.50
Purchase #6	$50.82	4.672%	$53.1943	$53.19	$53.20	$53.20
Purchase #7	$72.25	9.734%	$79.2828	$79.28	$79.30	$79.30
7 purchase totals =	$617.18		$662.4177	$662.41	$662.45	$662.50