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	$29.62	12.547%	$33.3364	$33.34	$33.35	$33.30
Purchase #2	$205.83	13.852%	$234.3416	$234.34	$234.35	$234.30
Purchase #3	$171.50	9.250%	$187.3638	$187.36	$187.35	$187.40
Purchase #4	$162.44	11.468%	$181.0686	$181.07	$181.05	$181.10
Purchase #5	$59.97	6.812%	$64.0552	$64.06	$64.05	$64.10
Purchase #6	$152.61	12.150%	$171.1521	$171.15	$171.15	$171.20
Purchase #7	$137.34	6.857%	$146.7574	$146.76	$146.75	$146.80
7 purchase totals =	$919.31		$1,018.0751	$1,018.08	$1,018.05	$1,018.20