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	$80.88	6.147%	$85.8517	$85.85	$85.85	$85.90
Purchase #2	$162.54	10.249%	$179.1987	$179.20	$179.20	$179.20
Purchase #3	$84.48	4.343%	$88.149	$88.15	$88.15	$88.10
Purchase #4	$39.53	10.639%	$43.7356	$43.74	$43.75	$43.70
Purchase #5	$173.52	10.547%	$191.8212	$191.82	$191.80	$191.80
Purchase #6	$207.61	13.682%	$236.0152	$236.02	$236.00	$236.00
Purchase #7	$116.61	6.262%	$123.9121	$123.91	$123.90	$123.90
7 purchase totals =	$865.17		$948.6835	$948.69	$948.65	$948.60