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	$162.51	5.862%	$172.0363	$172.04	$172.05	$172.00
Purchase #2	$64.77	8.289%	$70.1388	$70.14	$70.15	$70.10
Purchase #3	$219.39	12.750%	$247.3622	$247.36	$247.35	$247.40
Purchase #4	$148.69	12.480%	$167.2465	$167.25	$167.25	$167.20
Purchase #5	$69.84	12.177%	$78.3444	$78.34	$78.35	$78.30
Purchase #6	$176.97	8.432%	$191.8921	$191.89	$191.90	$191.90
Purchase #7	$167.72	3.150%	$173.0032	$173.00	$173.00	$173.00
7 purchase totals =	$1,009.89		$1,100.0235	$1,100.02	$1,100.05	$1,099.90