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	$243.31	11.642%	$271.6362	$271.64	$271.65	$271.60
Purchase #2	$9.43	13.706%	$10.7225	$10.72	$10.70	$10.70
Purchase #3	$56.73	5.668%	$59.9455	$59.95	$59.95	$59.90
Purchase #4	$213.64	10.163%	$235.3522	$235.35	$235.35	$235.40
Purchase #5	$165.77	12.540%	$186.5576	$186.56	$186.55	$186.60
Purchase #6	$82.36	8.136%	$89.0608	$89.06	$89.05	$89.10
Purchase #7	$73.36	9.110%	$80.0431	$80.04	$80.05	$80.00
7 purchase totals =	$844.60		$933.3179	$933.32	$933.30	$933.30