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	$154.94	7.239%	$166.1561	$166.16	$166.15	$166.20
Purchase #2	$195.95	9.130%	$213.8402	$213.84	$213.85	$213.80
Purchase #3	$67.35	8.200%	$72.8727	$72.87	$72.85	$72.90
Purchase #4	$170.60	3.645%	$176.8184	$176.82	$176.80	$176.80
Purchase #5	$146.25	12.323%	$164.2724	$164.27	$164.25	$164.30
Purchase #6	$94.75	4.653%	$99.1587	$99.16	$99.15	$99.20
Purchase #7	$193.32	3.331%	$199.7595	$199.76	$199.75	$199.80
7 purchase totals =	$1,023.16		$1,092.8780	$1,092.88	$1,092.80	$1,093.00