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	$147.98	4.503%	$154.6435	$154.64	$154.65	$154.60
Purchase #2	$204.86	4.264%	$213.5952	$213.60	$213.60	$213.60
Purchase #3	$164.94	9.722%	$180.9755	$180.98	$181.00	$181.00
Purchase #4	$139.74	9.415%	$152.8965	$152.90	$152.90	$152.90
Purchase #5	$96.63	3.609%	$100.1174	$100.12	$100.10	$100.10
Purchase #6	$38.28	13.335%	$43.3846	$43.38	$43.40	$43.40
Purchase #7	$148.74	6.133%	$157.8622	$157.86	$157.85	$157.90
7 purchase totals =	$941.17		$1,003.4749	$1,003.48	$1,003.50	$1,003.50