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	$154.87	5.198%	$162.9201	$162.92	$162.90	$162.90
Purchase #2	$132.36	11.424%	$147.4808	$147.48	$147.50	$147.50
Purchase #3	$202.76	13.446%	$230.0231	$230.02	$230.00	$230.00
Purchase #4	$192.73	3.860%	$200.1694	$200.17	$200.15	$200.20
Purchase #5	$82.64	7.708%	$89.0099	$89.01	$89.00	$89.00
Purchase #6	$83.70	3.127%	$86.3173	$86.32	$86.30	$86.30
Purchase #7	$176.64	4.874%	$185.2494	$185.25	$185.25	$185.20
7 purchase totals =	$1,025.70		$1,101.1700	$1,101.17	$1,101.10	$1,101.10