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	$167.88	4.468%	$175.3809	$175.38	$175.40	$175.40
Purchase #2	$40.68	4.461%	$42.4947	$42.49	$42.50	$42.50
Purchase #3	$39.42	7.805%	$42.4967	$42.50	$42.50	$42.50
Purchase #4	$104.93	6.583%	$111.8375	$111.84	$111.85	$111.80
Purchase #5	$160.29	12.550%	$180.4064	$180.41	$180.40	$180.40
Purchase #6	$216.65	13.685%	$246.2986	$246.30	$246.30	$246.30
Purchase #7	$215.64	12.430%	$242.4441	$242.44	$242.45	$242.40
7 purchase totals =	$945.49		$1,041.3589	$1,041.36	$1,041.40	$1,041.30