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	$149.52	4.588%	$156.38	$156.38	$156.40	$156.40
Purchase #2	$96.98	10.689%	$107.3462	$107.35	$107.35	$107.30
Purchase #3	$118.52	4.518%	$123.8747	$123.87	$123.85	$123.90
Purchase #4	$196.43	10.397%	$216.8528	$216.85	$216.85	$216.90
Purchase #5	$231.85	5.739%	$245.1559	$245.16	$245.15	$245.20
Purchase #6	$70.31	9.338%	$76.8755	$76.88	$76.90	$76.90
Purchase #7	$224.86	4.206%	$234.3176	$234.32	$234.30	$234.30
7 purchase totals =	$1,088.47		$1,160.8027	$1,160.81	$1,160.80	$1,160.90