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	$188.45	12.288%	$211.6067	$211.61	$211.60	$211.60
Purchase #2	$50.43	4.817%	$52.8592	$52.86	$52.85	$52.90
Purchase #3	$61.29	12.826%	$69.1511	$69.15	$69.15	$69.20
Purchase #4	$96.35	3.708%	$99.9227	$99.92	$99.90	$99.90
Purchase #5	$41.59	3.731%	$43.1417	$43.14	$43.15	$43.10
Purchase #6	$103.83	10.714%	$114.9543	$114.95	$114.95	$115.00
Purchase #7	$206.57	9.319%	$225.8203	$225.82	$225.80	$225.80
7 purchase totals =	$748.51		$817.4560	$817.45	$817.40	$817.50