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	$136.85	4.320%	$142.7619	$142.76	$142.75	$142.80
Purchase #2	$48.27	10.851%	$53.5078	$53.51	$53.50	$53.50
Purchase #3	$176.35	8.474%	$191.2939	$191.29	$191.30	$191.30
Purchase #4	$241.79	10.127%	$266.2761	$266.28	$266.30	$266.30
Purchase #5	$168.42	12.762%	$189.9138	$189.91	$189.90	$189.90
Purchase #6	$18.56	6.766%	$19.8158	$19.82	$19.80	$19.80
Purchase #7	$224.82	6.762%	$240.0223	$240.02	$240.00	$240.00
7 purchase totals =	$1,015.06		$1,103.5916	$1,103.59	$1,103.55	$1,103.60