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	$148.52	11.441%	$165.5122	$165.51	$165.50	$165.50
Purchase #2	$110.44	4.555%	$115.4705	$115.47	$115.45	$115.50
Purchase #3	$142.86	5.353%	$150.5073	$150.51	$150.50	$150.50
Purchase #4	$190.67	13.142%	$215.7279	$215.73	$215.75	$215.70
Purchase #5	$232.52	9.453%	$254.5001	$254.50	$254.50	$254.50
Purchase #6	$51.44	9.812%	$56.4873	$56.49	$56.50	$56.50
Purchase #7	$136.71	4.324%	$142.6213	$142.62	$142.60	$142.60
7 purchase totals =	$1,013.16		$1,100.8266	$1,100.83	$1,100.80	$1,100.80