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	$98.76	7.279%	$105.9487	$105.95	$105.95	$105.90
Purchase #2	$80.47	5.782%	$85.1228	$85.12	$85.10	$85.10
Purchase #3	$75.48	3.825%	$78.3671	$78.37	$78.35	$78.40
Purchase #4	$68.85	12.235%	$77.2738	$77.27	$77.25	$77.30
Purchase #5	$144.38	5.539%	$152.3772	$152.38	$152.40	$152.40
Purchase #6	$97.60	13.274%	$110.5554	$110.56	$110.55	$110.60
Purchase #7	$103.73	8.238%	$112.2753	$112.28	$112.30	$112.30
7 purchase totals =	$669.27		$721.9203	$721.93	$721.90	$722.00