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	$72.26	10.462%	$79.8198	$79.82	$79.80	$79.80
Purchase #2	$220.83	5.761%	$233.552	$233.55	$233.55	$233.60
Purchase #3	$26.52	3.199%	$27.3684	$27.37	$27.35	$27.40
Purchase #4	$76.67	11.224%	$85.2754	$85.28	$85.30	$85.30
Purchase #5	$157.83	9.507%	$172.8349	$172.83	$172.85	$172.80
Purchase #6	$167.92	10.721%	$185.9227	$185.92	$185.90	$185.90
Purchase #7	$200.33	12.835%	$226.0424	$226.04	$226.05	$226.00
7 purchase totals =	$922.36		$1,010.8156	$1,010.81	$1,010.80	$1,010.80