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	$93.41	7.453%	$100.3718	$100.37	$100.35	$100.40
Purchase #2	$208.29	8.354%	$225.6905	$225.69	$225.70	$225.70
Purchase #3	$93.63	8.217%	$101.3236	$101.32	$101.30	$101.30
Purchase #4	$107.69	3.759%	$111.7381	$111.74	$111.75	$111.70
Purchase #5	$223.74	5.687%	$236.4641	$236.46	$236.45	$236.50
Purchase #6	$98.68	11.371%	$109.9009	$109.90	$109.90	$109.90
Purchase #7	$54.26	6.122%	$57.5818	$57.58	$57.60	$57.60
7 purchase totals =	$879.70		$943.0708	$943.06	$943.05	$943.10