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	$249.72	10.826%	$276.7547	$276.75	$276.75	$276.80
Purchase #2	$62.35	11.305%	$69.3987	$69.40	$69.40	$69.40
Purchase #3	$181.30	8.435%	$196.5927	$196.59	$196.60	$196.60
Purchase #4	$238.61	5.103%	$250.7863	$250.79	$250.80	$250.80
Purchase #5	$191.32	10.423%	$211.2613	$211.26	$211.25	$211.30
Purchase #6	$43.95	12.722%	$49.5413	$49.54	$49.55	$49.50
Purchase #7	$65.48	5.555%	$69.1174	$69.12	$69.10	$69.10
7 purchase totals =	$1,032.73		$1,123.4524	$1,123.45	$1,123.45	$1,123.50