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	$90.74	7.378%	$97.4348	$97.43	$97.45	$97.40
Purchase #2	$235.36	9.866%	$258.5806	$258.58	$258.60	$258.60
Purchase #3	$156.69	9.503%	$171.5803	$171.58	$171.60	$171.60
Purchase #4	$63.78	13.347%	$72.2927	$72.29	$72.30	$72.30
Purchase #5	$145.29	7.441%	$156.101	$156.10	$156.10	$156.10
Purchase #6	$80.27	11.377%	$89.4023	$89.40	$89.40	$89.40
Purchase #7	$235.29	6.464%	$250.4991	$250.50	$250.50	$250.50
7 purchase totals =	$1,007.42		$1,095.8908	$1,095.88	$1,095.95	$1,095.90