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	$102.37	5.801%	$108.3085	$108.31	$108.30	$108.30
Purchase #2	$228.47	3.488%	$236.439	$236.44	$236.45	$236.40
Purchase #3	$96.40	9.266%	$105.3324	$105.33	$105.35	$105.30
Purchase #4	$90.80	5.195%	$95.5171	$95.52	$95.50	$95.50
Purchase #5	$100.30	9.731%	$110.0602	$110.06	$110.05	$110.10
Purchase #6	$179.57	7.771%	$193.5244	$193.52	$193.50	$193.50
Purchase #7	$180.71	9.839%	$198.4901	$198.49	$198.50	$198.50
7 purchase totals =	$978.62		$1,047.6717	$1,047.67	$1,047.65	$1,047.60