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	$162.38	11.593%	$181.2047	$181.20	$181.20	$181.20
Purchase #2	$38.88	9.505%	$42.5755	$42.58	$42.60	$42.60
Purchase #3	$137.57	6.130%	$146.003	$146.00	$146.00	$146.00
Purchase #4	$104.27	6.425%	$110.9693	$110.97	$110.95	$111.00
Purchase #5	$164.30	6.296%	$174.6443	$174.64	$174.65	$174.60
Purchase #6	$78.67	13.304%	$89.1363	$89.14	$89.15	$89.10
Purchase #7	$60.88	13.355%	$69.0105	$69.01	$69.00	$69.00
7 purchase totals =	$746.95		$813.5436	$813.54	$813.55	$813.50