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	$186.74	4.826%	$195.7521	$195.75	$195.75	$195.80
Purchase #2	$176.51	13.775%	$200.8243	$200.82	$200.80	$200.80
Purchase #3	$97.80	10.688%	$108.2529	$108.25	$108.25	$108.30
Purchase #4	$27.34	5.712%	$28.9017	$28.90	$28.90	$28.90
Purchase #5	$181.33	10.489%	$200.3497	$200.35	$200.35	$200.30
Purchase #6	$79.68	10.832%	$88.3109	$88.31	$88.30	$88.30
Purchase #7	$141.32	6.471%	$150.4648	$150.46	$150.45	$150.50
7 purchase totals =	$890.72		$972.8564	$972.84	$972.80	$972.90