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	$173.51	3.172%	$179.0137	$179.01	$179.00	$179.00
Purchase #2	$240.52	6.531%	$256.2284	$256.23	$256.25	$256.20
Purchase #3	$124.83	7.209%	$133.829	$133.83	$133.85	$133.80
Purchase #4	$178.29	4.571%	$186.4396	$186.44	$186.45	$186.40
Purchase #5	$147.44	3.723%	$152.9292	$152.93	$152.95	$152.90
Purchase #6	$145.82	9.402%	$159.53	$159.53	$159.55	$159.50
Purchase #7	$110.52	3.498%	$114.386	$114.39	$114.40	$114.40
7 purchase totals =	$1,120.93		$1,182.3559	$1,182.36	$1,182.45	$1,182.20