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	$139.45	12.857%	$157.3791	$157.38	$157.40	$157.40
Purchase #2	$181.56	4.763%	$190.2077	$190.21	$190.20	$190.20
Purchase #3	$159.74	4.109%	$166.3037	$166.30	$166.30	$166.30
Purchase #4	$99.59	10.247%	$109.795	$109.80	$109.80	$109.80
Purchase #5	$225.89	13.824%	$257.117	$257.12	$257.10	$257.10
Purchase #6	$167.87	8.570%	$182.2565	$182.26	$182.25	$182.30
Purchase #7	$44.92	3.627%	$46.5492	$46.55	$46.55	$46.50
7 purchase totals =	$1,019.02		$1,109.6082	$1,109.62	$1,109.60	$1,109.60