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	$86.37	7.596%	$92.9307	$92.93	$92.95	$92.90
Purchase #2	$236.93	11.781%	$264.8427	$264.84	$264.85	$264.80
Purchase #3	$119.76	9.558%	$131.2067	$131.21	$131.20	$131.20
Purchase #4	$118.91	7.227%	$127.5036	$127.50	$127.50	$127.50
Purchase #5	$231.88	13.778%	$263.8284	$263.83	$263.85	$263.80
Purchase #6	$231.72	11.484%	$258.3307	$258.33	$258.35	$258.30
Purchase #7	$12.53	10.177%	$13.8052	$13.81	$13.80	$13.80
7 purchase totals =	$1,038.10		$1,152.4480	$1,152.45	$1,152.50	$1,152.30