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	$96.89	3.340%	$100.1261	$100.13	$100.15	$100.10
Purchase #2	$94.64	6.676%	$100.9582	$100.96	$100.95	$101.00
Purchase #3	$58.67	7.596%	$63.1266	$63.13	$63.15	$63.10
Purchase #4	$145.32	13.107%	$164.3671	$164.37	$164.35	$164.40
Purchase #5	$180.64	3.215%	$186.4476	$186.45	$186.45	$186.40
Purchase #6	$76.52	11.800%	$85.5494	$85.55	$85.55	$85.50
Purchase #7	$179.52	8.444%	$194.6787	$194.68	$194.70	$194.70
7 purchase totals =	$832.20		$895.2537	$895.27	$895.30	$895.20