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	$243.56	8.122%	$263.3419	$263.34	$263.35	$263.30
Purchase #2	$17.56	4.311%	$18.317	$18.32	$18.30	$18.30
Purchase #3	$211.94	12.105%	$237.5953	$237.60	$237.60	$237.60
Purchase #4	$185.50	3.714%	$192.3895	$192.39	$192.40	$192.40
Purchase #5	$206.37	7.727%	$222.3162	$222.32	$222.30	$222.30
Purchase #6	$42.37	6.869%	$45.2804	$45.28	$45.30	$45.30
Purchase #7	$63.50	12.424%	$71.3892	$71.39	$71.40	$71.40
7 purchase totals =	$970.80		$1,050.6295	$1,050.64	$1,050.65	$1,050.60