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	$78.61	4.557%	$82.1923	$82.19	$82.20	$82.20
Purchase #2	$96.43	9.349%	$105.4452	$105.45	$105.45	$105.40
Purchase #3	$86.72	10.780%	$96.0684	$96.07	$96.05	$96.10
Purchase #4	$45.94	10.147%	$50.6015	$50.60	$50.60	$50.60
Purchase #5	$212.95	9.592%	$233.3762	$233.38	$233.40	$233.40
Purchase #6	$31.38	7.847%	$33.8424	$33.84	$33.85	$33.80
Purchase #7	$100.80	9.380%	$110.255	$110.26	$110.25	$110.30
7 purchase totals =	$652.83		$711.7810	$711.79	$711.80	$711.80