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	$98.59	13.119%	$111.524	$111.52	$111.50	$111.50
Purchase #2	$78.38	6.650%	$83.5923	$83.59	$83.60	$83.60
Purchase #3	$194.99	5.735%	$206.1727	$206.17	$206.15	$206.20
Purchase #4	$76.93	4.192%	$80.1549	$80.15	$80.15	$80.20
Purchase #5	$166.86	6.567%	$177.8177	$177.82	$177.80	$177.80
Purchase #6	$229.40	7.197%	$245.9099	$245.91	$245.90	$245.90
Purchase #7	$59.76	7.833%	$64.441	$64.44	$64.45	$64.40
7 purchase totals =	$904.91		$969.6125	$969.60	$969.55	$969.60