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	$141.82	6.787%	$151.4453	$151.45	$151.45	$151.40
Purchase #2	$208.36	12.195%	$233.7695	$233.77	$233.75	$233.80
Purchase #3	$223.74	4.270%	$233.2937	$233.29	$233.30	$233.30
Purchase #4	$24.76	12.773%	$27.9226	$27.92	$27.90	$27.90
Purchase #5	$56.45	10.608%	$62.4382	$62.44	$62.45	$62.40
Purchase #6	$186.62	12.177%	$209.3447	$209.34	$209.35	$209.30
Purchase #7	$180.87	3.440%	$187.0919	$187.09	$187.10	$187.10
7 purchase totals =	$1,022.62		$1,105.3059	$1,105.30	$1,105.30	$1,105.20