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	$92.62	11.679%	$103.4371	$103.44	$103.45	$103.40
Purchase #2	$82.66	8.222%	$89.4563	$89.46	$89.45	$89.50
Purchase #3	$12.97	7.506%	$13.9435	$13.94	$13.95	$13.90
Purchase #4	$103.48	8.517%	$112.2934	$112.29	$112.30	$112.30
Purchase #5	$126.82	12.130%	$142.2033	$142.20	$142.20	$142.20
Purchase #6	$147.59	12.685%	$166.3118	$166.31	$166.30	$166.30
Purchase #7	$38.79	7.494%	$41.6969	$41.70	$41.70	$41.70
7 purchase totals =	$604.93		$669.3423	$669.34	$669.35	$669.30