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	$228.27	5.355%	$240.4939	$240.49	$240.50	$240.50
Purchase #2	$6.97	3.659%	$7.225	$7.23	$7.25	$7.20
Purchase #3	$56.33	11.808%	$62.9814	$62.98	$63.00	$63.00
Purchase #4	$150.51	5.134%	$158.2372	$158.24	$158.25	$158.20
Purchase #5	$91.88	12.608%	$103.4642	$103.46	$103.45	$103.50
Purchase #6	$42.68	9.824%	$46.8729	$46.87	$46.85	$46.90
Purchase #7	$197.90	10.328%	$218.3391	$218.34	$218.35	$218.30
7 purchase totals =	$774.54		$837.6137	$837.61	$837.65	$837.60