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	$131.40	10.398%	$145.063	$145.06	$145.05	$145.10
Purchase #2	$221.69	10.785%	$245.5993	$245.60	$245.60	$245.60
Purchase #3	$178.61	4.388%	$186.4474	$186.45	$186.45	$186.40
Purchase #4	$27.33	10.693%	$30.2524	$30.25	$30.25	$30.30
Purchase #5	$83.75	7.250%	$89.8219	$89.82	$89.80	$89.80
Purchase #6	$165.85	12.151%	$186.0024	$186.00	$186.00	$186.00
Purchase #7	$105.95	12.864%	$119.5794	$119.58	$119.60	$119.60
7 purchase totals =	$914.58		$1,002.7658	$1,002.76	$1,002.75	$1,002.80