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	$40.71	9.258%	$44.4789	$44.48	$44.50	$44.50
Purchase #2	$160.32	8.642%	$174.1749	$174.17	$174.15	$174.20
Purchase #3	$88.74	12.779%	$100.0801	$100.08	$100.10	$100.10
Purchase #4	$147.41	6.365%	$156.7926	$156.79	$156.80	$156.80
Purchase #5	$190.46	10.291%	$210.0602	$210.06	$210.05	$210.10
Purchase #6	$222.97	3.323%	$230.3793	$230.38	$230.40	$230.40
Purchase #7	$90.79	10.139%	$99.9952	$100.00	$100.00	$100.00
7 purchase totals =	$941.40		$1,015.9612	$1,015.96	$1,016.00	$1,016.10