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	$144.76	12.765%	$163.2386	$163.24	$163.25	$163.20
Purchase #2	$156.43	10.500%	$172.8552	$172.86	$172.85	$172.90
Purchase #3	$92.47	3.400%	$95.614	$95.61	$95.60	$95.60
Purchase #4	$73.66	10.326%	$81.2661	$81.27	$81.25	$81.30
Purchase #5	$236.44	7.799%	$254.88	$254.88	$254.90	$254.90
Purchase #6	$228.92	13.212%	$259.1649	$259.16	$259.15	$259.20
Purchase #7	$64.65	4.107%	$67.3052	$67.31	$67.30	$67.30
7 purchase totals =	$997.33		$1,094.3240	$1,094.33	$1,094.30	$1,094.40