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	$96.75	8.565%	$105.0366	$105.04	$105.05	$105.00
Purchase #2	$47.53	5.873%	$50.3214	$50.32	$50.30	$50.30
Purchase #3	$210.79	6.686%	$224.8834	$224.88	$224.90	$224.90
Purchase #4	$230.85	8.650%	$250.8185	$250.82	$250.80	$250.80
Purchase #5	$181.73	5.367%	$191.4834	$191.48	$191.50	$191.50
Purchase #6	$155.60	6.826%	$166.2213	$166.22	$166.20	$166.20
Purchase #7	$216.64	6.322%	$230.336	$230.34	$230.35	$230.30
7 purchase totals =	$1,139.89		$1,219.1006	$1,219.10	$1,219.10	$1,219.00