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	$167.86	6.170%	$178.217	$178.22	$178.20	$178.20
Purchase #2	$228.42	3.600%	$236.6431	$236.64	$236.65	$236.60
Purchase #3	$85.36	3.780%	$88.5866	$88.59	$88.60	$88.60
Purchase #4	$193.73	6.144%	$205.6328	$205.63	$205.65	$205.60
Purchase #5	$75.45	3.121%	$77.8048	$77.80	$77.80	$77.80
Purchase #6	$108.51	13.632%	$123.3021	$123.30	$123.30	$123.30
Purchase #7	$53.61	10.380%	$59.1747	$59.17	$59.15	$59.20
7 purchase totals =	$912.94		$969.3611	$969.35	$969.35	$969.30