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	$202.57	6.865%	$216.4764	$216.48	$216.50	$216.50
Purchase #2	$97.29	12.364%	$109.3189	$109.32	$109.30	$109.30
Purchase #3	$47.27	4.504%	$49.399	$49.40	$49.40	$49.40
Purchase #4	$120.95	9.851%	$132.8648	$132.86	$132.85	$132.90
Purchase #5	$237.78	11.287%	$264.6182	$264.62	$264.60	$264.60
Purchase #6	$97.29	13.595%	$110.5166	$110.52	$110.50	$110.50
Purchase #7	$233.57	12.675%	$263.175	$263.18	$263.20	$263.20
7 purchase totals =	$1,036.72		$1,146.3689	$1,146.38	$1,146.35	$1,146.40