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	$190.26	9.670%	$208.6581	$208.66	$208.65	$208.70
Purchase #2	$102.31	7.123%	$109.5975	$109.60	$109.60	$109.60
Purchase #3	$245.34	6.308%	$260.816	$260.82	$260.80	$260.80
Purchase #4	$77.57	7.207%	$83.1605	$83.16	$83.15	$83.20
Purchase #5	$105.28	4.222%	$109.7249	$109.72	$109.70	$109.70
Purchase #6	$160.84	11.501%	$179.3382	$179.34	$179.35	$179.30
Purchase #7	$58.37	10.262%	$64.3599	$64.36	$64.35	$64.40
7 purchase totals =	$939.97		$1,015.6551	$1,015.66	$1,015.60	$1,015.70