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	$187.85	3.422%	$194.2782	$194.28	$194.30	$194.30
Purchase #2	$5.31	9.820%	$5.8314	$5.83	$5.85	$5.80
Purchase #3	$84.84	13.250%	$96.0813	$96.08	$96.10	$96.10
Purchase #4	$168.46	9.820%	$185.0028	$185.00	$185.00	$185.00
Purchase #5	$230.64	12.691%	$259.9105	$259.91	$259.90	$259.90
Purchase #6	$177.83	10.579%	$196.6426	$196.64	$196.65	$196.60
Purchase #7	$57.98	5.467%	$61.1498	$61.15	$61.15	$61.10
7 purchase totals =	$912.91		$998.8966	$998.89	$998.95	$998.80