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	$166.44	11.688%	$185.8935	$185.89	$185.90	$185.90
Purchase #2	$55.34	11.121%	$61.4944	$61.49	$61.50	$61.50
Purchase #3	$5.41	12.715%	$6.0979	$6.10	$6.10	$6.10
Purchase #4	$227.34	9.289%	$248.4576	$248.46	$248.45	$248.50
Purchase #5	$138.32	7.431%	$148.5986	$148.60	$148.60	$148.60
Purchase #6	$173.56	7.481%	$186.544	$186.54	$186.55	$186.50
Purchase #7	$185.73	10.511%	$205.2521	$205.25	$205.25	$205.30
7 purchase totals =	$952.14		$1,042.3381	$1,042.33	$1,042.35	$1,042.40