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	$215.33	11.717%	$240.5602	$240.56	$240.55	$240.60
Purchase #2	$238.69	5.338%	$251.4313	$251.43	$251.45	$251.40
Purchase #3	$170.97	11.264%	$190.2281	$190.23	$190.25	$190.20
Purchase #4	$9.54	3.380%	$9.8625	$9.86	$9.85	$9.90
Purchase #5	$67.62	7.500%	$72.6915	$72.69	$72.70	$72.70
Purchase #6	$19.92	3.173%	$20.5521	$20.55	$20.55	$20.60
Purchase #7	$228.53	4.199%	$238.126	$238.13	$238.15	$238.10
7 purchase totals =	$950.60		$1,023.4517	$1,023.45	$1,023.50	$1,023.50