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	$41.64	6.216%	$44.2283	$44.23	$44.25	$44.20
Purchase #2	$73.75	6.465%	$78.5179	$78.52	$78.50	$78.50
Purchase #3	$169.79	7.737%	$182.9267	$182.93	$182.95	$182.90
Purchase #4	$62.54	3.834%	$64.9378	$64.94	$64.95	$64.90
Purchase #5	$66.35	10.402%	$73.2517	$73.25	$73.25	$73.30
Purchase #6	$85.74	11.129%	$95.282	$95.28	$95.30	$95.30
Purchase #7	$63.29	7.356%	$67.9456	$67.95	$67.95	$67.90
7 purchase totals =	$563.10		$607.0900	$607.10	$607.15	$607.00