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	$201.53	10.333%	$222.3541	$222.35	$222.35	$222.40
Purchase #2	$178.80	4.810%	$187.4003	$187.40	$187.40	$187.40
Purchase #3	$174.50	3.350%	$180.3458	$180.35	$180.35	$180.30
Purchase #4	$61.82	10.714%	$68.4434	$68.44	$68.45	$68.40
Purchase #5	$91.98	12.539%	$103.5134	$103.51	$103.50	$103.50
Purchase #6	$244.33	4.357%	$254.9755	$254.98	$255.00	$255.00
Purchase #7	$72.43	10.518%	$80.0482	$80.05	$80.05	$80.00
7 purchase totals =	$1,025.39		$1,097.0807	$1,097.08	$1,097.10	$1,097.00