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	$162.72	12.178%	$182.536	$182.54	$182.55	$182.50
Purchase #2	$110.28	12.280%	$123.8224	$123.82	$123.80	$123.80
Purchase #3	$109.92	12.618%	$123.7897	$123.79	$123.80	$123.80
Purchase #4	$166.94	7.326%	$179.17	$179.17	$179.15	$179.20
Purchase #5	$125.39	12.255%	$140.7565	$140.76	$140.75	$140.80
Purchase #6	$146.61	4.223%	$152.8013	$152.80	$152.80	$152.80
Purchase #7	$86.60	11.534%	$96.5884	$96.59	$96.60	$96.60
7 purchase totals =	$908.46		$999.4643	$999.47	$999.45	$999.50