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	$50.99	5.184%	$53.6333	$53.63	$53.65	$53.60
Purchase #2	$46.29	12.410%	$52.0346	$52.03	$52.05	$52.00
Purchase #3	$160.67	11.301%	$178.8273	$178.83	$178.85	$178.80
Purchase #4	$59.75	5.174%	$62.8415	$62.84	$62.85	$62.80
Purchase #5	$191.72	7.603%	$206.2965	$206.30	$206.30	$206.30
Purchase #6	$11.36	4.690%	$11.8928	$11.89	$11.90	$11.90
Purchase #7	$176.88	11.240%	$196.7613	$196.76	$196.75	$196.80
7 purchase totals =	$697.66		$762.2873	$762.28	$762.35	$762.20