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	$168.89	3.849%	$175.3906	$175.39	$175.40	$175.40
Purchase #2	$245.46	12.731%	$276.7095	$276.71	$276.70	$276.70
Purchase #3	$164.44	3.575%	$170.3187	$170.32	$170.30	$170.30
Purchase #4	$59.41	13.398%	$67.3698	$67.37	$67.35	$67.40
Purchase #5	$145.54	13.497%	$165.1835	$165.18	$165.20	$165.20
Purchase #6	$48.45	11.226%	$53.889	$53.89	$53.90	$53.90
Purchase #7	$118.27	13.650%	$134.4139	$134.41	$134.40	$134.40
7 purchase totals =	$950.46		$1,043.2750	$1,043.27	$1,043.25	$1,043.30