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	$183.62	4.469%	$191.826	$191.83	$191.85	$191.80
Purchase #2	$155.72	9.346%	$170.2736	$170.27	$170.25	$170.30
Purchase #3	$108.76	10.605%	$120.294	$120.29	$120.30	$120.30
Purchase #4	$122.83	4.193%	$127.9803	$127.98	$128.00	$128.00
Purchase #5	$130.49	6.809%	$139.3751	$139.38	$139.40	$139.40
Purchase #6	$180.72	7.558%	$194.3788	$194.38	$194.40	$194.40
Purchase #7	$213.95	11.399%	$238.3382	$238.34	$238.35	$238.30
7 purchase totals =	$1,096.09		$1,182.4660	$1,182.47	$1,182.55	$1,182.50