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	$233.76	9.480%	$255.9204	$255.92	$255.90	$255.90
Purchase #2	$245.56	3.421%	$253.9606	$253.96	$253.95	$254.00
Purchase #3	$186.37	6.763%	$198.9742	$198.97	$198.95	$199.00
Purchase #4	$192.74	6.560%	$205.3837	$205.38	$205.40	$205.40
Purchase #5	$173.54	6.774%	$185.2956	$185.30	$185.30	$185.30
Purchase #6	$119.95	6.640%	$127.9147	$127.91	$127.90	$127.90
Purchase #7	$34.93	9.597%	$38.2822	$38.28	$38.30	$38.30
7 purchase totals =	$1,186.85		$1,265.7314	$1,265.72	$1,265.70	$1,265.80