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	$99.92	13.188%	$113.0974	$113.10	$113.10	$113.10
Purchase #2	$197.88	13.602%	$224.7956	$224.80	$224.80	$224.80
Purchase #3	$156.50	8.207%	$169.344	$169.34	$169.35	$169.30
Purchase #4	$52.69	13.508%	$59.8074	$59.81	$59.80	$59.80
Purchase #5	$66.34	7.616%	$71.3925	$71.39	$71.40	$71.40
Purchase #6	$185.37	5.775%	$196.0751	$196.08	$196.10	$196.10
Purchase #7	$245.63	13.527%	$278.8564	$278.86	$278.85	$278.90
7 purchase totals =	$1,004.33		$1,113.3684	$1,113.38	$1,113.40	$1,113.40