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	$134.34	10.787%	$148.8313	$148.83	$148.85	$148.80
Purchase #2	$160.69	6.740%	$171.5205	$171.52	$171.50	$171.50
Purchase #3	$38.26	8.141%	$41.3747	$41.37	$41.35	$41.40
Purchase #4	$91.82	5.832%	$97.1749	$97.17	$97.15	$97.20
Purchase #5	$127.90	11.329%	$142.3898	$142.39	$142.40	$142.40
Purchase #6	$20.83	10.614%	$23.0409	$23.04	$23.05	$23.00
Purchase #7	$135.49	5.334%	$142.717	$142.72	$142.70	$142.70
7 purchase totals =	$709.33		$767.0491	$767.04	$767.00	$767.00