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	$183.31	4.475%	$191.5131	$191.51	$191.50	$191.50
Purchase #2	$73.98	12.355%	$83.1202	$83.12	$83.10	$83.10
Purchase #3	$87.86	12.319%	$98.6835	$98.68	$98.70	$98.70
Purchase #4	$82.91	9.253%	$90.5817	$90.58	$90.60	$90.60
Purchase #5	$39.34	13.683%	$44.7229	$44.72	$44.70	$44.70
Purchase #6	$89.72	7.282%	$96.2534	$96.25	$96.25	$96.30
Purchase #7	$94.30	10.259%	$103.9742	$103.97	$103.95	$104.00
7 purchase totals =	$651.42		$708.8490	$708.83	$708.80	$708.90