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	$148.33	6.730%	$158.3126	$158.31	$158.30	$158.30
Purchase #2	$192.30	10.228%	$211.9684	$211.97	$211.95	$212.00
Purchase #3	$42.44	4.754%	$44.4576	$44.46	$44.45	$44.50
Purchase #4	$90.63	10.591%	$100.2286	$100.23	$100.25	$100.20
Purchase #5	$88.83	8.350%	$96.2473	$96.25	$96.25	$96.20
Purchase #6	$206.78	7.461%	$222.2079	$222.21	$222.20	$222.20
Purchase #7	$111.41	4.656%	$116.5972	$116.60	$116.60	$116.60
7 purchase totals =	$880.72		$950.0196	$950.03	$950.00	$950.00