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	$135.86	5.144%	$142.8486	$142.85	$142.85	$142.80
Purchase #2	$67.45	4.700%	$70.6202	$70.62	$70.60	$70.60
Purchase #3	$138.40	11.391%	$154.1651	$154.17	$154.15	$154.20
Purchase #4	$172.27	4.136%	$179.3951	$179.40	$179.40	$179.40
Purchase #5	$230.44	8.185%	$249.3015	$249.30	$249.30	$249.30
Purchase #6	$154.71	10.533%	$171.0056	$171.01	$171.00	$171.00
Purchase #7	$199.47	9.333%	$218.0865	$218.09	$218.10	$218.10
7 purchase totals =	$1,098.60		$1,185.4226	$1,185.44	$1,185.40	$1,185.40