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	$181.89	5.747%	$192.3432	$192.34	$192.35	$192.30
Purchase #2	$140.82	9.377%	$154.0247	$154.02	$154.00	$154.00
Purchase #3	$135.45	4.845%	$142.0126	$142.01	$142.00	$142.00
Purchase #4	$139.92	13.414%	$158.6889	$158.69	$158.70	$158.70
Purchase #5	$123.66	11.297%	$137.6299	$137.63	$137.65	$137.60
Purchase #6	$207.33	13.573%	$235.4709	$235.47	$235.45	$235.50
Purchase #7	$81.61	11.839%	$91.2718	$91.27	$91.25	$91.30
7 purchase totals =	$1,010.68		$1,111.4420	$1,111.43	$1,111.40	$1,111.40