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	$148.82	10.694%	$164.7348	$164.73	$164.75	$164.70
Purchase #2	$147.53	3.436%	$152.5991	$152.60	$152.60	$152.60
Purchase #3	$168.85	13.477%	$191.6059	$191.61	$191.60	$191.60
Purchase #4	$54.54	3.254%	$56.3147	$56.31	$56.30	$56.30
Purchase #5	$250.54	10.444%	$276.7064	$276.71	$276.70	$276.70
Purchase #6	$234.70	11.442%	$261.5544	$261.55	$261.55	$261.60
Purchase #7	$162.29	6.426%	$172.7188	$172.72	$172.70	$172.70
7 purchase totals =	$1,167.27		$1,276.2341	$1,276.23	$1,276.20	$1,276.20