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	$46.59	8.380%	$50.4942	$50.49	$50.50	$50.50
Purchase #2	$198.37	13.805%	$225.755	$225.76	$225.75	$225.80
Purchase #3	$156.59	6.818%	$167.2663	$167.27	$167.25	$167.30
Purchase #4	$183.57	6.478%	$195.4617	$195.46	$195.45	$195.50
Purchase #5	$93.27	3.342%	$96.3871	$96.39	$96.40	$96.40
Purchase #6	$30.28	5.417%	$31.9203	$31.92	$31.90	$31.90
Purchase #7	$156.59	6.665%	$167.0267	$167.03	$167.05	$167.00
7 purchase totals =	$865.26		$934.3113	$934.32	$934.30	$934.40