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	$218.41	9.235%	$238.5802	$238.58	$238.60	$238.60
Purchase #2	$88.52	10.649%	$97.9465	$97.95	$97.95	$97.90
Purchase #3	$133.97	6.481%	$142.6526	$142.65	$142.65	$142.70
Purchase #4	$26.53	8.710%	$28.8408	$28.84	$28.85	$28.80
Purchase #5	$114.27	11.360%	$127.2511	$127.25	$127.25	$127.30
Purchase #6	$171.76	8.143%	$185.7464	$185.75	$185.75	$185.70
Purchase #7	$27.70	13.294%	$31.3824	$31.38	$31.40	$31.40
7 purchase totals =	$781.16		$852.4000	$852.40	$852.45	$852.40