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	$92.34	13.156%	$104.4883	$104.49	$104.50	$104.50
Purchase #2	$95.75	13.242%	$108.4292	$108.43	$108.45	$108.40
Purchase #3	$211.98	5.854%	$224.3893	$224.39	$224.40	$224.40
Purchase #4	$221.58	8.524%	$240.4675	$240.47	$240.45	$240.50
Purchase #5	$136.58	7.516%	$146.8454	$146.85	$146.85	$146.80
Purchase #6	$96.85	13.297%	$109.7281	$109.73	$109.75	$109.70
Purchase #7	$171.89	3.740%	$178.3187	$178.32	$178.30	$178.30
7 purchase totals =	$1,026.97		$1,112.6665	$1,112.68	$1,112.70	$1,112.60