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	$86.65	12.640%	$97.6026	$97.60	$97.60	$97.60
Purchase #2	$178.39	10.187%	$196.5626	$196.56	$196.55	$196.60
Purchase #3	$170.74	6.171%	$181.2764	$181.28	$181.30	$181.30
Purchase #4	$75.88	5.221%	$79.8417	$79.84	$79.85	$79.80
Purchase #5	$105.60	10.851%	$117.0587	$117.06	$117.05	$117.10
Purchase #6	$126.87	3.370%	$131.1455	$131.15	$131.15	$131.10
Purchase #7	$141.50	4.799%	$148.2906	$148.29	$148.30	$148.30
7 purchase totals =	$885.63		$951.7781	$951.78	$951.80	$951.80