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	$157.31	4.441%	$164.2961	$164.30	$164.30	$164.30
Purchase #2	$228.78	7.274%	$245.4215	$245.42	$245.40	$245.40
Purchase #3	$82.77	4.474%	$86.4731	$86.47	$86.45	$86.50
Purchase #4	$142.39	6.544%	$151.708	$151.71	$151.70	$151.70
Purchase #5	$237.99	11.672%	$265.7682	$265.77	$265.75	$265.80
Purchase #6	$89.39	12.853%	$100.8793	$100.88	$100.90	$100.90
Purchase #7	$237.51	10.693%	$262.9069	$262.91	$262.90	$262.90
7 purchase totals =	$1,176.14		$1,277.4531	$1,277.46	$1,277.40	$1,277.50