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	$200.73	10.729%	$222.2663	$222.27	$222.25	$222.30
Purchase #2	$221.76	3.211%	$228.8807	$228.88	$228.90	$228.90
Purchase #3	$58.47	5.515%	$61.6946	$61.69	$61.70	$61.70
Purchase #4	$123.90	5.865%	$131.1667	$131.17	$131.15	$131.20
Purchase #5	$140.37	9.570%	$153.8034	$153.80	$153.80	$153.80
Purchase #6	$101.97	12.793%	$115.015	$115.02	$115.00	$115.00
Purchase #7	$146.37	7.300%	$157.055	$157.06	$157.05	$157.10
7 purchase totals =	$993.57		$1,069.8817	$1,069.89	$1,069.85	$1,070.00