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	$35.49	4.832%	$37.2049	$37.20	$37.20	$37.20
Purchase #2	$118.77	3.839%	$123.3296	$123.33	$123.35	$123.30
Purchase #3	$52.27	4.396%	$54.5678	$54.57	$54.55	$54.60
Purchase #4	$7.57	3.427%	$7.8294	$7.83	$7.85	$7.80
Purchase #5	$217.96	9.145%	$237.8924	$237.89	$237.90	$237.90
Purchase #6	$239.33	12.376%	$268.9495	$268.95	$268.95	$268.90
Purchase #7	$210.96	10.775%	$233.6909	$233.69	$233.70	$233.70
7 purchase totals =	$882.35		$963.4645	$963.46	$963.50	$963.40