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	$57.62	3.626%	$59.7093	$59.71	$59.70	$59.70
Purchase #2	$176.75	6.661%	$188.5233	$188.52	$188.50	$188.50
Purchase #3	$196.45	13.282%	$222.5425	$222.54	$222.55	$222.50
Purchase #4	$43.99	3.523%	$45.5398	$45.54	$45.55	$45.50
Purchase #5	$165.27	10.551%	$182.7076	$182.71	$182.70	$182.70
Purchase #6	$182.72	13.467%	$207.3269	$207.33	$207.35	$207.30
Purchase #7	$66.84	12.869%	$75.4416	$75.44	$75.45	$75.40
7 purchase totals =	$889.64		$981.7910	$981.79	$981.80	$981.60