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	$191.97	3.343%	$198.3876	$198.39	$198.40	$198.40
Purchase #2	$157.92	6.309%	$167.8832	$167.88	$167.90	$167.90
Purchase #3	$146.89	5.567%	$155.0674	$155.07	$155.05	$155.10
Purchase #4	$115.72	6.551%	$123.3008	$123.30	$123.30	$123.30
Purchase #5	$9.94	3.740%	$10.3118	$10.31	$10.30	$10.30
Purchase #6	$230.67	5.473%	$243.2946	$243.29	$243.30	$243.30
Purchase #7	$95.32	10.618%	$105.4411	$105.44	$105.45	$105.40
7 purchase totals =	$948.43		$1,003.6865	$1,003.68	$1,003.70	$1,003.70