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	$155.84	7.453%	$167.4548	$167.45	$167.45	$167.50
Purchase #2	$117.96	11.119%	$131.076	$131.08	$131.10	$131.10
Purchase #3	$156.61	5.303%	$164.915	$164.92	$164.90	$164.90
Purchase #4	$155.38	7.858%	$167.5898	$167.59	$167.60	$167.60
Purchase #5	$9.63	4.424%	$10.056	$10.06	$10.05	$10.10
Purchase #6	$145.73	5.846%	$154.2494	$154.25	$154.25	$154.20
Purchase #7	$142.98	8.597%	$155.272	$155.27	$155.25	$155.30
7 purchase totals =	$884.13		$950.6130	$950.62	$950.60	$950.70