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	$162.40	6.872%	$173.5601	$173.56	$173.55	$173.60
Purchase #2	$127.71	11.236%	$142.0595	$142.06	$142.05	$142.10
Purchase #3	$75.67	6.416%	$80.525	$80.53	$80.55	$80.50
Purchase #4	$169.96	3.746%	$176.3267	$176.33	$176.35	$176.30
Purchase #5	$26.39	10.859%	$29.2557	$29.26	$29.25	$29.30
Purchase #6	$169.28	5.729%	$178.9781	$178.98	$179.00	$179.00
Purchase #7	$205.52	8.841%	$223.69	$223.69	$223.70	$223.70
7 purchase totals =	$936.93		$1,004.3951	$1,004.41	$1,004.45	$1,004.50