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	$72.31	8.396%	$78.3811	$78.38	$78.40	$78.40
Purchase #2	$174.63	13.519%	$198.2382	$198.24	$198.25	$198.20
Purchase #3	$37.84	3.506%	$39.1667	$39.17	$39.15	$39.20
Purchase #4	$180.42	9.827%	$198.1499	$198.15	$198.15	$198.10
Purchase #5	$86.80	11.376%	$96.6744	$96.67	$96.65	$96.70
Purchase #6	$54.82	4.789%	$57.4453	$57.45	$57.45	$57.40
Purchase #7	$12.76	11.194%	$14.1884	$14.19	$14.20	$14.20
7 purchase totals =	$619.58		$682.2440	$682.25	$682.25	$682.20