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	$222.45	10.729%	$246.3167	$246.32	$246.30	$246.30
Purchase #2	$196.34	7.102%	$210.2841	$210.28	$210.30	$210.30
Purchase #3	$208.57	6.784%	$222.7194	$222.72	$222.70	$222.70
Purchase #4	$215.33	11.811%	$240.7626	$240.76	$240.75	$240.80
Purchase #5	$103.45	12.769%	$116.6595	$116.66	$116.65	$116.70
Purchase #6	$79.82	7.557%	$85.852	$85.85	$85.85	$85.90
Purchase #7	$43.71	9.455%	$47.8428	$47.84	$47.85	$47.80
7 purchase totals =	$1,069.67		$1,170.4371	$1,170.43	$1,170.40	$1,170.50