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	$202.42	3.475%	$209.4541	$209.45	$209.45	$209.50
Purchase #2	$67.83	3.127%	$69.951	$69.95	$69.95	$70.00
Purchase #3	$214.55	4.632%	$224.488	$224.49	$224.50	$224.50
Purchase #4	$86.75	3.392%	$89.6926	$89.69	$89.70	$89.70
Purchase #5	$191.85	6.384%	$204.0977	$204.10	$204.10	$204.10
Purchase #6	$59.45	13.809%	$67.6595	$67.66	$67.65	$67.70
Purchase #7	$64.90	11.497%	$72.3616	$72.36	$72.35	$72.40
7 purchase totals =	$887.75		$937.7045	$937.70	$937.70	$937.90