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	$29.98	13.187%	$33.9335	$33.93	$33.95	$33.90
Purchase #2	$196.96	6.169%	$209.1105	$209.11	$209.10	$209.10
Purchase #3	$222.72	6.307%	$236.767	$236.77	$236.75	$236.80
Purchase #4	$231.76	4.622%	$242.4719	$242.47	$242.45	$242.50
Purchase #5	$52.98	4.130%	$55.1681	$55.17	$55.15	$55.20
Purchase #6	$155.77	10.262%	$171.7551	$171.76	$171.75	$171.80
Purchase #7	$73.45	5.181%	$77.2554	$77.26	$77.25	$77.30
7 purchase totals =	$963.62		$1,026.4615	$1,026.47	$1,026.40	$1,026.60