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	$92.97	13.851%	$105.8473	$105.85	$105.85	$105.80
Purchase #2	$193.43	3.550%	$200.2968	$200.30	$200.30	$200.30
Purchase #3	$47.58	11.406%	$53.007	$53.01	$53.00	$53.00
Purchase #4	$235.68	13.167%	$266.712	$266.71	$266.70	$266.70
Purchase #5	$223.39	5.370%	$235.386	$235.39	$235.40	$235.40
Purchase #6	$54.75	12.568%	$61.631	$61.63	$61.65	$61.60
Purchase #7	$198.42	10.280%	$218.8176	$218.82	$218.80	$218.80
7 purchase totals =	$1,046.22		$1,141.6977	$1,141.71	$1,141.70	$1,141.60