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	$178.60	3.754%	$185.3046	$185.30	$185.30	$185.30
Purchase #2	$57.47	4.287%	$59.9337	$59.93	$59.95	$59.90
Purchase #3	$215.37	3.290%	$222.4557	$222.46	$222.45	$222.50
Purchase #4	$36.85	11.438%	$41.0649	$41.06	$41.05	$41.10
Purchase #5	$153.84	13.326%	$174.3407	$174.34	$174.35	$174.30
Purchase #6	$184.91	12.560%	$208.1347	$208.13	$208.15	$208.10
Purchase #7	$238.45	7.585%	$256.5364	$256.54	$256.55	$256.50
7 purchase totals =	$1,065.49		$1,147.7707	$1,147.76	$1,147.80	$1,147.70