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	$159.38	5.696%	$168.4583	$168.46	$168.45	$168.50
Purchase #2	$236.49	6.121%	$250.9656	$250.97	$250.95	$251.00
Purchase #3	$46.34	13.182%	$52.4485	$52.45	$52.45	$52.40
Purchase #4	$160.37	4.769%	$168.018	$168.02	$168.00	$168.00
Purchase #5	$91.89	3.372%	$94.9885	$94.99	$95.00	$95.00
Purchase #6	$189.36	13.670%	$215.2455	$215.25	$215.25	$215.20
Purchase #7	$122.31	4.467%	$127.7736	$127.77	$127.75	$127.80
7 purchase totals =	$1,006.14		$1,077.8980	$1,077.91	$1,077.85	$1,077.90