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	$220.25	13.671%	$250.3604	$250.36	$250.35	$250.40
Purchase #2	$180.57	11.205%	$200.8029	$200.80	$200.80	$200.80
Purchase #3	$154.69	4.323%	$161.3772	$161.38	$161.40	$161.40
Purchase #4	$61.81	4.682%	$64.7039	$64.70	$64.70	$64.70
Purchase #5	$149.91	11.411%	$167.0162	$167.02	$167.00	$167.00
Purchase #6	$88.63	3.156%	$91.4272	$91.43	$91.45	$91.40
Purchase #7	$142.50	5.666%	$150.5741	$150.57	$150.55	$150.60
7 purchase totals =	$998.36		$1,086.2619	$1,086.26	$1,086.25	$1,086.30