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	$141.48	7.198%	$151.6637	$151.66	$151.65	$151.70
Purchase #2	$156.67	5.352%	$165.055	$165.06	$165.05	$165.10
Purchase #3	$201.34	12.240%	$225.984	$225.98	$226.00	$226.00
Purchase #4	$173.44	4.871%	$181.8883	$181.89	$181.90	$181.90
Purchase #5	$36.32	3.441%	$37.5698	$37.57	$37.55	$37.60
Purchase #6	$85.67	5.688%	$90.5429	$90.54	$90.55	$90.50
Purchase #7	$5.61	12.235%	$6.2964	$6.30	$6.30	$6.30
7 purchase totals =	$800.53		$859.0001	$859.00	$859.00	$859.10