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	$64.77	11.510%	$72.225	$72.23	$72.25	$72.20
Purchase #2	$228.81	9.153%	$249.753	$249.75	$249.75	$249.80
Purchase #3	$206.62	10.505%	$228.3254	$228.33	$228.35	$228.30
Purchase #4	$203.50	12.693%	$229.3303	$229.33	$229.35	$229.30
Purchase #5	$79.25	3.159%	$81.7535	$81.75	$81.75	$81.80
Purchase #6	$47.86	6.559%	$50.9991	$51.00	$51.00	$51.00
Purchase #7	$97.57	3.152%	$100.6454	$100.65	$100.65	$100.60
7 purchase totals =	$928.38		$1,013.0317	$1,013.04	$1,013.10	$1,013.00