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	$135.80	4.627%	$142.0835	$142.08	$142.10	$142.10
Purchase #2	$40.59	11.695%	$45.337	$45.34	$45.35	$45.30
Purchase #3	$75.80	3.784%	$78.6683	$78.67	$78.65	$78.70
Purchase #4	$211.67	11.849%	$236.7508	$236.75	$236.75	$236.80
Purchase #5	$165.49	7.786%	$178.3751	$178.38	$178.40	$178.40
Purchase #6	$172.71	3.145%	$178.1417	$178.14	$178.15	$178.10
Purchase #7	$137.79	4.628%	$144.1669	$144.17	$144.15	$144.20
7 purchase totals =	$939.85		$1,003.5233	$1,003.53	$1,003.55	$1,003.60