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	$187.94	4.390%	$196.1906	$196.19	$196.20	$196.20
Purchase #2	$174.34	9.800%	$191.4253	$191.43	$191.45	$191.40
Purchase #3	$225.76	11.788%	$252.3726	$252.37	$252.35	$252.40
Purchase #4	$225.88	6.860%	$241.3754	$241.38	$241.40	$241.40
Purchase #5	$247.28	5.815%	$261.6593	$261.66	$261.65	$261.70
Purchase #6	$64.32	5.278%	$67.7148	$67.71	$67.70	$67.70
Purchase #7	$148.37	8.267%	$160.6357	$160.64	$160.65	$160.60
7 purchase totals =	$1,273.89		$1,371.3737	$1,371.38	$1,371.40	$1,371.40