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	$179.29	5.660%	$189.4378	$189.44	$189.45	$189.40
Purchase #2	$28.72	3.821%	$29.8174	$29.82	$29.80	$29.80
Purchase #3	$31.36	4.349%	$32.7238	$32.72	$32.70	$32.70
Purchase #4	$42.35	6.705%	$45.1896	$45.19	$45.20	$45.20
Purchase #5	$172.50	11.155%	$191.7424	$191.74	$191.75	$191.70
Purchase #6	$91.47	3.675%	$94.8315	$94.83	$94.85	$94.80
Purchase #7	$183.29	8.212%	$198.3418	$198.34	$198.35	$198.30
7 purchase totals =	$728.98		$782.0843	$782.08	$782.10	$781.90