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	$92.81	7.333%	$99.6158	$99.62	$99.60	$99.60
Purchase #2	$250.63	12.572%	$282.1392	$282.14	$282.15	$282.10
Purchase #3	$179.67	3.862%	$186.6089	$186.61	$186.60	$186.60
Purchase #4	$116.30	7.309%	$124.8004	$124.80	$124.80	$124.80
Purchase #5	$72.33	12.396%	$81.296	$81.30	$81.30	$81.30
Purchase #6	$141.75	4.615%	$148.2918	$148.29	$148.30	$148.30
Purchase #7	$84.67	5.334%	$89.1863	$89.19	$89.20	$89.20
7 purchase totals =	$938.16		$1,011.9384	$1,011.95	$1,011.95	$1,011.90