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	$207.99	13.649%	$236.3786	$236.38	$236.40	$236.40
Purchase #2	$98.25	11.398%	$109.4485	$109.45	$109.45	$109.40
Purchase #3	$187.76	6.319%	$199.6246	$199.62	$199.60	$199.60
Purchase #4	$233.61	11.409%	$260.2626	$260.26	$260.25	$260.30
Purchase #5	$72.54	13.747%	$82.5121	$82.51	$82.50	$82.50
Purchase #6	$73.58	6.585%	$78.4252	$78.43	$78.45	$78.40
Purchase #7	$101.40	4.698%	$106.1638	$106.16	$106.15	$106.20
7 purchase totals =	$975.13		$1,072.8154	$1,072.81	$1,072.80	$1,072.80