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	$173.46	5.849%	$183.6057	$183.61	$183.60	$183.60
Purchase #2	$94.83	3.326%	$97.984	$97.98	$98.00	$98.00
Purchase #3	$181.47	4.453%	$189.5509	$189.55	$189.55	$189.60
Purchase #4	$41.68	4.426%	$43.5248	$43.52	$43.50	$43.50
Purchase #5	$78.64	4.849%	$82.4533	$82.45	$82.45	$82.50
Purchase #6	$147.92	7.616%	$159.1856	$159.19	$159.20	$159.20
Purchase #7	$166.87	8.429%	$180.9355	$180.94	$180.95	$180.90
7 purchase totals =	$884.87		$937.2398	$937.24	$937.25	$937.30