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	$107.59	4.471%	$112.4003	$112.40	$112.40	$112.40
Purchase #2	$65.65	7.710%	$70.7116	$70.71	$70.70	$70.70
Purchase #3	$179.98	8.850%	$195.9082	$195.91	$195.90	$195.90
Purchase #4	$203.98	3.373%	$210.8602	$210.86	$210.85	$210.90
Purchase #5	$243.54	6.700%	$259.8572	$259.86	$259.85	$259.90
Purchase #6	$26.63	8.481%	$28.8885	$28.89	$28.90	$28.90
Purchase #7	$53.59	10.171%	$59.0406	$59.04	$59.05	$59.00
7 purchase totals =	$880.96		$937.6666	$937.67	$937.65	$937.70