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	$100.98	10.192%	$111.2719	$111.27	$111.25	$111.30
Purchase #2	$70.82	4.321%	$73.8801	$73.88	$73.90	$73.90
Purchase #3	$137.65	9.448%	$150.6552	$150.66	$150.65	$150.70
Purchase #4	$202.87	12.459%	$228.1456	$228.15	$228.15	$228.10
Purchase #5	$187.32	12.571%	$210.868	$210.87	$210.85	$210.90
Purchase #6	$89.48	13.456%	$101.5204	$101.52	$101.50	$101.50
Purchase #7	$161.82	10.489%	$178.7933	$178.79	$178.80	$178.80
7 purchase totals =	$950.94		$1,055.1345	$1,055.14	$1,055.10	$1,055.20