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	$77.99	9.127%	$85.1081	$85.11	$85.10	$85.10
Purchase #2	$79.35	13.356%	$89.948	$89.95	$89.95	$89.90
Purchase #3	$196.83	6.622%	$209.8641	$209.86	$209.85	$209.90
Purchase #4	$243.26	5.374%	$256.3328	$256.33	$256.35	$256.30
Purchase #5	$224.72	4.304%	$234.3919	$234.39	$234.40	$234.40
Purchase #6	$86.59	3.737%	$89.8259	$89.83	$89.85	$89.80
Purchase #7	$51.34	9.694%	$56.3169	$56.32	$56.30	$56.30
7 purchase totals =	$960.08		$1,021.7877	$1,021.79	$1,021.80	$1,021.70