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	$38.92	5.680%	$41.1307	$41.13	$41.15	$41.10
Purchase #2	$17.56	6.155%	$18.6408	$18.64	$18.65	$18.60
Purchase #3	$195.64	10.247%	$215.6872	$215.69	$215.70	$215.70
Purchase #4	$75.58	13.537%	$85.8113	$85.81	$85.80	$85.80
Purchase #5	$78.25	7.191%	$83.877	$83.88	$83.90	$83.90
Purchase #6	$234.77	6.330%	$249.6309	$249.63	$249.65	$249.60
Purchase #7	$240.46	4.242%	$250.6603	$250.66	$250.65	$250.70
7 purchase totals =	$881.18		$945.4382	$945.44	$945.50	$945.40