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	$82.92	9.750%	$91.0047	$91.00	$91.00	$91.00
Purchase #2	$103.88	3.454%	$107.468	$107.47	$107.45	$107.50
Purchase #3	$136.86	7.123%	$146.6085	$146.61	$146.60	$146.60
Purchase #4	$180.93	10.706%	$200.3004	$200.30	$200.30	$200.30
Purchase #5	$82.63	7.779%	$89.0578	$89.06	$89.05	$89.10
Purchase #6	$84.96	13.129%	$96.1144	$96.11	$96.10	$96.10
Purchase #7	$21.56	5.845%	$22.8202	$22.82	$22.80	$22.80
7 purchase totals =	$693.74		$753.3740	$753.37	$753.30	$753.40