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	$65.26	9.329%	$71.3481	$71.35	$71.35	$71.30
Purchase #2	$159.94	13.399%	$181.3704	$181.37	$181.35	$181.40
Purchase #3	$19.25	5.802%	$20.3669	$20.37	$20.35	$20.40
Purchase #4	$185.84	10.390%	$205.1488	$205.15	$205.15	$205.10
Purchase #5	$137.91	10.411%	$152.2678	$152.27	$152.25	$152.30
Purchase #6	$200.88	12.839%	$226.671	$226.67	$226.65	$226.70
Purchase #7	$204.33	7.250%	$219.1439	$219.14	$219.15	$219.10
7 purchase totals =	$973.41		$1,076.3169	$1,076.32	$1,076.25	$1,076.30