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	$200.82	10.591%	$222.0888	$222.09	$222.10	$222.10
Purchase #2	$194.53	6.348%	$206.8788	$206.88	$206.90	$206.90
Purchase #3	$188.72	8.844%	$205.4104	$205.41	$205.40	$205.40
Purchase #4	$92.33	10.381%	$101.9148	$101.91	$101.90	$101.90
Purchase #5	$74.88	4.471%	$78.2279	$78.23	$78.25	$78.20
Purchase #6	$174.86	9.492%	$191.4577	$191.46	$191.45	$191.50
Purchase #7	$248.45	13.615%	$282.2765	$282.28	$282.30	$282.30
7 purchase totals =	$1,174.59		$1,288.2549	$1,288.26	$1,288.30	$1,288.30