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	$50.49	7.330%	$54.1909	$54.19	$54.20	$54.20
Purchase #2	$138.46	11.758%	$154.7401	$154.74	$154.75	$154.70
Purchase #3	$92.78	10.817%	$102.816	$102.82	$102.80	$102.80
Purchase #4	$74.52	5.102%	$78.322	$78.32	$78.30	$78.30
Purchase #5	$117.79	5.148%	$123.8538	$123.85	$123.85	$123.90
Purchase #6	$170.80	4.380%	$178.281	$178.28	$178.30	$178.30
Purchase #7	$28.80	11.855%	$32.2142	$32.21	$32.20	$32.20
7 purchase totals =	$673.64		$724.4180	$724.41	$724.40	$724.40