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	$43.34	3.408%	$44.817	$44.82	$44.80	$44.80
Purchase #2	$63.25	4.626%	$66.1759	$66.18	$66.20	$66.20
Purchase #3	$100.90	8.218%	$109.192	$109.19	$109.20	$109.20
Purchase #4	$105.32	11.333%	$117.2559	$117.26	$117.25	$117.30
Purchase #5	$222.68	5.700%	$235.3728	$235.37	$235.35	$235.40
Purchase #6	$79.46	4.310%	$82.8847	$82.88	$82.90	$82.90
Purchase #7	$8.35	5.645%	$8.8214	$8.82	$8.80	$8.80
7 purchase totals =	$623.30		$664.5197	$664.52	$664.50	$664.60