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	$101.52	3.289%	$104.859	$104.86	$104.85	$104.90
Purchase #2	$241.64	9.395%	$264.3421	$264.34	$264.35	$264.30
Purchase #3	$99.71	3.131%	$102.8319	$102.83	$102.85	$102.80
Purchase #4	$219.66	4.693%	$229.9686	$229.97	$229.95	$230.00
Purchase #5	$173.32	4.865%	$181.752	$181.75	$181.75	$181.80
Purchase #6	$186.81	4.316%	$194.8727	$194.87	$194.85	$194.90
Purchase #7	$11.52	11.354%	$12.828	$12.83	$12.85	$12.80
7 purchase totals =	$1,034.18		$1,091.4543	$1,091.45	$1,091.45	$1,091.50