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	$128.54	11.156%	$142.8799	$142.88	$142.90	$142.90
Purchase #2	$131.90	9.498%	$144.4279	$144.43	$144.45	$144.40
Purchase #3	$173.56	10.257%	$191.362	$191.36	$191.35	$191.40
Purchase #4	$244.58	7.512%	$262.9528	$262.95	$262.95	$263.00
Purchase #5	$134.32	11.587%	$149.8837	$149.88	$149.90	$149.90
Purchase #6	$236.84	11.252%	$263.4892	$263.49	$263.50	$263.50
Purchase #7	$156.93	9.747%	$172.226	$172.23	$172.25	$172.20
7 purchase totals =	$1,206.67		$1,327.2215	$1,327.22	$1,327.30	$1,327.30