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	$178.83	6.286%	$190.0713	$190.07	$190.05	$190.10
Purchase #2	$83.83	7.345%	$89.9873	$89.99	$90.00	$90.00
Purchase #3	$33.31	12.734%	$37.5517	$37.55	$37.55	$37.60
Purchase #4	$172.52	10.567%	$190.7502	$190.75	$190.75	$190.80
Purchase #5	$90.38	6.844%	$96.5656	$96.57	$96.55	$96.60
Purchase #6	$16.88	12.358%	$18.966	$18.97	$18.95	$19.00
Purchase #7	$100.51	9.427%	$109.9851	$109.99	$110.00	$110.00
7 purchase totals =	$676.26		$733.8772	$733.89	$733.85	$734.10