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	$101.75	8.874%	$110.7793	$110.78	$110.80	$110.80
Purchase #2	$113.34	12.410%	$127.4055	$127.41	$127.40	$127.40
Purchase #3	$200.47	10.581%	$221.6817	$221.68	$221.70	$221.70
Purchase #4	$182.34	7.828%	$196.6136	$196.61	$196.60	$196.60
Purchase #5	$60.25	11.731%	$67.3179	$67.32	$67.30	$67.30
Purchase #6	$99.95	10.293%	$110.2379	$110.24	$110.25	$110.20
Purchase #7	$162.42	12.365%	$182.5032	$182.50	$182.50	$182.50
7 purchase totals =	$920.52		$1,016.5391	$1,016.54	$1,016.55	$1,016.50