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	$166.45	3.672%	$172.562	$172.56	$172.55	$172.60
Purchase #2	$75.76	10.275%	$83.5443	$83.54	$83.55	$83.50
Purchase #3	$207.80	4.609%	$217.3775	$217.38	$217.40	$217.40
Purchase #4	$174.50	11.290%	$194.2011	$194.20	$194.20	$194.20
Purchase #5	$147.38	10.437%	$162.7621	$162.76	$162.75	$162.80
Purchase #6	$119.31	6.772%	$127.3897	$127.39	$127.40	$127.40
Purchase #7	$180.81	12.490%	$203.3932	$203.39	$203.40	$203.40
7 purchase totals =	$1,072.01		$1,161.2299	$1,161.22	$1,161.25	$1,161.30