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	$169.36	11.751%	$189.2615	$189.26	$189.25	$189.30
Purchase #2	$151.79	11.852%	$169.7802	$169.78	$169.80	$169.80
Purchase #3	$132.56	9.845%	$145.6105	$145.61	$145.60	$145.60
Purchase #4	$18.33	11.179%	$20.3791	$20.38	$20.40	$20.40
Purchase #5	$156.68	12.236%	$175.8514	$175.85	$175.85	$175.90
Purchase #6	$100.45	9.442%	$109.9345	$109.93	$109.95	$109.90
Purchase #7	$207.89	8.640%	$225.8517	$225.85	$225.85	$225.90
7 purchase totals =	$937.06		$1,036.6689	$1,036.66	$1,036.70	$1,036.80