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	$226.27	9.808%	$248.4626	$248.46	$248.45	$248.50
Purchase #2	$167.48	4.161%	$174.4488	$174.45	$174.45	$174.40
Purchase #3	$133.98	5.411%	$141.2297	$141.23	$141.25	$141.20
Purchase #4	$177.35	3.407%	$183.3923	$183.39	$183.40	$183.40
Purchase #5	$19.59	12.442%	$22.0274	$22.03	$22.05	$22.00
Purchase #6	$95.92	9.858%	$105.3758	$105.38	$105.40	$105.40
Purchase #7	$118.28	8.120%	$127.8843	$127.88	$127.90	$127.90
7 purchase totals =	$938.87		$1,002.8209	$1,002.82	$1,002.90	$1,002.80