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	$87.32	4.138%	$90.9333	$90.93	$90.95	$90.90
Purchase #2	$150.98	3.356%	$156.0469	$156.05	$156.05	$156.00
Purchase #3	$49.48	8.380%	$53.6264	$53.63	$53.65	$53.60
Purchase #4	$224.91	13.399%	$255.0457	$255.05	$255.05	$255.00
Purchase #5	$240.97	3.520%	$249.4521	$249.45	$249.45	$249.50
Purchase #6	$79.82	3.828%	$82.8755	$82.88	$82.90	$82.90
Purchase #7	$125.55	13.342%	$142.3009	$142.30	$142.30	$142.30
7 purchase totals =	$959.03		$1,030.2808	$1,030.29	$1,030.35	$1,030.20