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	$114.33	11.182%	$127.1144	$127.11	$127.10	$127.10
Purchase #2	$207.99	9.578%	$227.9113	$227.91	$227.90	$227.90
Purchase #3	$163.43	4.352%	$170.5425	$170.54	$170.55	$170.50
Purchase #4	$128.40	13.535%	$145.7789	$145.78	$145.80	$145.80
Purchase #5	$185.93	11.818%	$207.9032	$207.90	$207.90	$207.90
Purchase #6	$38.83	8.342%	$42.0692	$42.07	$42.05	$42.10
Purchase #7	$177.64	3.730%	$184.266	$184.27	$184.25	$184.30
7 purchase totals =	$1,016.55		$1,105.5855	$1,105.58	$1,105.55	$1,105.60