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	$224.32	9.489%	$245.6057	$245.61	$245.60	$245.60
Purchase #2	$127.34	11.584%	$142.0911	$142.09	$142.10	$142.10
Purchase #3	$141.35	10.868%	$156.7119	$156.71	$156.70	$156.70
Purchase #4	$138.55	5.330%	$145.9347	$145.93	$145.95	$145.90
Purchase #5	$186.71	7.285%	$200.3118	$200.31	$200.30	$200.30
Purchase #6	$39.81	3.531%	$41.2157	$41.22	$41.20	$41.20
Purchase #7	$159.86	11.576%	$178.3654	$178.37	$178.35	$178.40
7 purchase totals =	$1,017.94		$1,110.2363	$1,110.24	$1,110.20	$1,110.20