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	$134.73	9.247%	$147.1885	$147.19	$147.20	$147.20
Purchase #2	$139.44	5.226%	$146.7271	$146.73	$146.75	$146.70
Purchase #3	$152.98	6.254%	$162.5474	$162.55	$162.55	$162.50
Purchase #4	$185.71	7.315%	$199.2947	$199.29	$199.30	$199.30
Purchase #5	$108.36	8.755%	$117.8469	$117.85	$117.85	$117.80
Purchase #6	$115.40	10.538%	$127.5609	$127.56	$127.55	$127.60
Purchase #7	$218.64	10.420%	$241.4223	$241.42	$241.40	$241.40
7 purchase totals =	$1,055.26		$1,142.5878	$1,142.59	$1,142.60	$1,142.50