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	$98.69	12.390%	$110.9177	$110.92	$110.90	$110.90
Purchase #2	$109.82	3.447%	$113.6055	$113.61	$113.60	$113.60
Purchase #3	$141.67	4.555%	$148.1231	$148.12	$148.10	$148.10
Purchase #4	$170.55	7.721%	$183.7182	$183.72	$183.70	$183.70
Purchase #5	$154.80	13.604%	$175.859	$175.86	$175.85	$175.90
Purchase #6	$75.82	7.747%	$81.6938	$81.69	$81.70	$81.70
Purchase #7	$188.47	4.438%	$196.8343	$196.83	$196.85	$196.80
7 purchase totals =	$939.82		$1,010.7516	$1,010.75	$1,010.70	$1,010.70