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	$68.68	4.148%	$71.5288	$71.53	$71.55	$71.50
Purchase #2	$72.31	9.767%	$79.3725	$79.37	$79.35	$79.40
Purchase #3	$169.49	6.380%	$180.3035	$180.30	$180.30	$180.30
Purchase #4	$90.49	7.757%	$97.5093	$97.51	$97.50	$97.50
Purchase #5	$54.35	9.372%	$59.4437	$59.44	$59.45	$59.40
Purchase #6	$109.48	12.786%	$123.4781	$123.48	$123.50	$123.50
Purchase #7	$218.93	13.571%	$248.641	$248.64	$248.65	$248.60
7 purchase totals =	$783.73		$860.2769	$860.27	$860.30	$860.20