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	$155.56	12.234%	$174.5912	$174.59	$174.60	$174.60
Purchase #2	$31.31	11.265%	$34.8371	$34.84	$34.85	$34.80
Purchase #3	$41.59	6.617%	$44.342	$44.34	$44.35	$44.30
Purchase #4	$187.31	9.402%	$204.9209	$204.92	$204.90	$204.90
Purchase #5	$165.72	7.432%	$178.0363	$178.04	$178.05	$178.00
Purchase #6	$218.37	11.376%	$243.2118	$243.21	$243.20	$243.20
Purchase #7	$18.45	10.805%	$20.4435	$20.44	$20.45	$20.40
7 purchase totals =	$818.31		$900.3828	$900.38	$900.40	$900.20