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	$99.59	11.493%	$111.0359	$111.04	$111.05	$111.00
Purchase #2	$193.70	9.595%	$212.2855	$212.29	$212.30	$212.30
Purchase #3	$59.39	6.592%	$63.305	$63.31	$63.30	$63.30
Purchase #4	$63.97	13.606%	$72.6738	$72.67	$72.65	$72.70
Purchase #5	$165.73	13.427%	$187.9826	$187.98	$188.00	$188.00
Purchase #6	$75.55	13.467%	$85.7243	$85.72	$85.70	$85.70
Purchase #7	$41.27	5.299%	$43.4569	$43.46	$43.45	$43.50
7 purchase totals =	$699.20		$776.4640	$776.47	$776.45	$776.50