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	$204.88	8.230%	$221.7416	$221.74	$221.75	$221.70
Purchase #2	$38.88	10.792%	$43.0759	$43.08	$43.10	$43.10
Purchase #3	$81.27	5.373%	$85.6366	$85.64	$85.65	$85.60
Purchase #4	$105.59	3.568%	$109.3575	$109.36	$109.35	$109.40
Purchase #5	$242.50	4.854%	$254.271	$254.27	$254.25	$254.30
Purchase #6	$55.58	7.802%	$59.9164	$59.92	$59.90	$59.90
Purchase #7	$47.60	3.239%	$49.1418	$49.14	$49.15	$49.10
7 purchase totals =	$776.30		$823.1408	$823.15	$823.15	$823.10