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	$160.41	3.713%	$166.366	$166.37	$166.35	$166.40
Purchase #2	$176.82	8.210%	$191.3369	$191.34	$191.35	$191.30
Purchase #3	$63.70	11.427%	$70.979	$70.98	$71.00	$71.00
Purchase #4	$79.64	7.184%	$85.3613	$85.36	$85.35	$85.40
Purchase #5	$6.40	13.386%	$7.2567	$7.26	$7.25	$7.30
Purchase #6	$28.60	11.398%	$31.8598	$31.86	$31.85	$31.90
Purchase #7	$187.98	11.358%	$209.3308	$209.33	$209.35	$209.30
7 purchase totals =	$703.55		$762.4905	$762.50	$762.50	$762.60