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	$69.92	10.107%	$76.9868	$76.99	$77.00	$77.00
Purchase #2	$69.33	13.790%	$78.8906	$78.89	$78.90	$78.90
Purchase #3	$142.41	6.848%	$152.1622	$152.16	$152.15	$152.20
Purchase #4	$229.96	8.670%	$249.8975	$249.90	$249.90	$249.90
Purchase #5	$28.42	10.812%	$31.4928	$31.49	$31.50	$31.50
Purchase #6	$111.53	10.820%	$123.5975	$123.60	$123.60	$123.60
Purchase #7	$207.68	10.570%	$229.6318	$229.63	$229.65	$229.60
7 purchase totals =	$859.25		$942.6592	$942.66	$942.70	$942.70