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	$100.29	9.732%	$110.0502	$110.05	$110.05	$110.10
Purchase #2	$171.46	5.768%	$181.3498	$181.35	$181.35	$181.30
Purchase #3	$54.38	11.790%	$60.7914	$60.79	$60.80	$60.80
Purchase #4	$238.89	8.532%	$259.2721	$259.27	$259.25	$259.30
Purchase #5	$245.71	13.619%	$279.1732	$279.17	$279.15	$279.20
Purchase #6	$81.36	5.839%	$86.1106	$86.11	$86.10	$86.10
Purchase #7	$124.53	6.608%	$132.7589	$132.76	$132.75	$132.80
7 purchase totals =	$1,016.62		$1,109.5062	$1,109.50	$1,109.45	$1,109.60